Learn Hardcore Spanish (Latin America): Este año mi mayor desafío es practicar todos los días, aunque solo tenga diez minutos libres. - This year my biggest challenge is to practice every day, even if I only have ten free minutes.

Aunque tengo diez minutos libres (indicative):
- The speaker treats it as a known, real fact.
- Nuance: even though I (definitely) have ten minutes free…
Aunque tenga diez minutos libres (subjunctive, as in the sentence):
- The speaker is talking about a possible or variable situation.
- Nuance: even if I (only) have ten minutes free…
  It suggests that sometimes they may have those ten minutes, sometimes not, or they are imagining the situation in general.

In your sentence, the idea is more like a general commitment:
…practicar todos los días, aunque solo tenga diez minutos libres
= …to practice every day, even if I only have ten free minutes.

Why is it es practicar and not es practico or es practicando?

In Spanish, when you define what something is (its nature, purpose, or main difficulty), you normally use the infinitive as a noun-like form.

Mi mayor desafío es practicar todos los días.
Literally: My biggest challenge is to practice every day.
Functionally, it matches English My biggest challenge is practicing every day.

Compare:

Es importante practicar. – It is important to practice.
Mi objetivo es aprender más. – My goal is to learn more.

Using practico (present tense) would be incorrect here:

Mi mayor desafío es practico – ungrammatical.

Using practicando also sounds wrong in this structure:

Mi mayor desafío es practicando – ungrammatical.

So after es in this type of sentence (biggest challenge, goal, problem, etc.), you almost always use the infinitive: es practicar, es aprender, es organizarme, etc.

What is the difference between solo and sólo here? Is the accent needed?

Traditionally:

sólo (with accent) = adverb = only
solo (without accent) = adjective = alone

However, the current recommendation from the Royal Spanish Academy (RAE) is:

Write solo without an accent in almost all cases.
Only use sólo with an accent if there is real ambiguity (and even then, many writers still don’t use the accent).

In your sentence:

aunque solo tenga diez minutos libres
Meaning: even if I only have ten free minutes

Here, solo is clearly the adverb only, and there is no ambiguity with alone, so modern standard practice is to write it without an accent.

In Latin America, you may still see sólo with accent in some texts, but solo is perfectly correct and increasingly preferred.

Can I move solo to a different position? Does the meaning change?

You have some flexibility with solo, and all of these are grammatically correct:

Aunque solo tenga diez minutos libres.
Most common, neutral.
Focus: I only have ten free minutes.
Aunque tenga solo diez minutos libres.
Slight extra emphasis on solo; often used in speech for contrast.
Focus: the quantity is small (only ten minutes).
Aunque tenga diez minutos libres solo.
This sounds odd or ambiguous. It can be interpreted as:
- I have ten minutes free alone (by myself), not just only ten minutes. So here solo tends to be heard as alone, not only.

So, in practice:

To say only, keep solo before the verb or the number:
solo tenga… or tenga solo diez minutos…
Avoid putting solo at the very end unless you really mean alone.

Why is it minutos libres and not tiempo libre?

Both expressions exist, but they are used differently:

tiempo libre = free time in general, as a mass concept.
- No tengo mucho tiempo libre. – I don’t have much free time.
minutos libres = free minutes, a specific amount of time.
- Solo tengo diez minutos libres. – I only have ten free minutes.

In your sentence, the idea is a precise, small amount of time, so diez minutos libres fits perfectly.

Also note how libres agrees in number and gender with minutos:

un minuto libre
diez minutos libres
una hora libre
tres horas libres

Why is it todos los días instead of cada día or todos días?

todos los días vs cada día

Both are correct:

practicar todos los días – to practice every day
practicar cada día – to practice each day / every day

Nuance:

todos los días is more common and neutral.
cada día can sound a bit more emphatic or literary in some contexts, but it is also normal in everyday speech.

Why not todos días?

Because in Spanish, todos (all/every) with a plural noun normally needs a definite article:

todos los días – all the days / every day
todas las semanas – every week
todos los años – every year

So todos días is ungrammatical; you must say todos los días.

What does mayor mean in mi mayor desafío? Does it refer to age?

Mayor does often mean older when talking about age:

mi hermano mayor – my older brother
mi hija mayor – my eldest daughter

But mayor also has a more general meaning: bigger, greater, more important, main, chief.

In mi mayor desafío it means:

my biggest challenge
my greatest challenge
my main challenge

You could also say:

mi desafío más grande – my biggest challenge

Both mi mayor desafío and mi desafío más grande are correct and natural.
Mayor here is a bit more concise and commonly used in written or slightly formal speech.

Do we need a preposition before este año? Could we say en este año?

In most cases describing something happening this year as a general time frame, you do not use a preposition:

Este año mi mayor desafío es practicar todos los días.
This year my biggest challenge is to practice every day.

This is the standard, natural way to say it.

En este año is not wrong, but it tends to be used when you are contrasting years or emphasizing the specific time period:

En este año hemos logrado muchas cosas, más que en años anteriores.

So for a simple statement like your sentence, Este año… (no preposition) is the normal choice.

Could we say aunque solo tengo diez minutos libres instead of aunque solo tenga? How would the meaning change?

Yes, you can say both, but they are not identical in nuance.

Aunque solo tengo diez minutos libres (indicative):
- The speaker treats the situation as a known, real fact.
- Roughly: even though I only have ten free minutes.
- It can suggest: that is the current, concrete situation.
Aunque solo tenga diez minutos libres (subjunctive, original):
- The speaker describes a possible, variable, or hypothetical condition.
- Roughly: even if I only have ten free minutes.
- It sounds more like a general rule or commitment, regardless of how much time there will actually be each day.

In context of a New Year–type resolution (statement about the whole year), the subjunctive tenga fits very well because it talks about an ongoing or general condition: whatever the case each day, even if it is just ten minutes.

Is desafío the usual word in Latin America, or would reto or meta sound better?

All three words are common, but they are not exact synonyms:

desafío – challenge, something difficult that tests you.
Very common and natural in Latin America in this kind of sentence.
reto – also challenge; often used similarly to desafío.
In some countries, reto can feel a bit more colloquial or sporty (like a challenge between people), but usage varies a lot by region.
meta – goal or target (something you want to achieve), not the difficulty itself.
- Mi meta este año es practicar todos los días.
  My goal this year is to practice every day.

Your sentence focuses on the difficulty, so desafío is a very good and natural choice in Latin American Spanish:

Mi mayor desafío es practicar todos los días. – My biggest challenge is to practice every day.