A veces me cuesta distinguir la verdad de la mentira.

A veces means sometimes.

It is very common to place it at the beginning of the sentence to set the scene right away:

• A veces me cuesta... = Sometimes it’s hard for me...

You could also hear:

• Me cuesta a veces distinguir...

But A veces at the start sounds very natural and clear.

Spanish often uses costar to express that something is difficult or takes effort.

Literally, costar means to cost, but in sentences like this it means something more like:

• to be hard for someone
• to take effort
• to be difficult

So:

• Me cuesta distinguir... = I find it hard to distinguish...

A very literal breakdown would be:

• me = to me / for me
• cuesta = is difficult / costs effort
• distinguir... = to distinguish...

This structure is extremely common in Spanish:

• Me cuesta dormir. = I have trouble sleeping.
• Le cuesta entenderlo. = It’s hard for him/her to understand it.

Me is an indirect object pronoun meaning to me or for me.

So:

• Me cuesta = It is hard for me
• Te cuesta = It is hard for you
• Le cuesta = It is hard for him/her

The person who experiences the difficulty is shown with this pronoun.

Compare:

• Me cuesta estudiar. = Studying is hard for me.
• Nos cuesta levantarnos temprano. = Getting up early is hard for us.

So me is not the subject. It marks the person affected.

Because the subject is not yo.

In this sentence, the thing that is difficult is the action distinguir la verdad de la mentira. That whole infinitive phrase functions as the subject, and Spanish normally uses third person singular with that kind of subject:

• Me cuesta distinguir...
• Te cuesta aceptar...
• Nos cuesta creer...

So cuesta agrees with the action, not with the person.

If you said cuesto, that would mean I cost, which is not what you want here.

Because after costar, Spanish normally uses an infinitive to say what is hard to do.

Structure:

• costarle a alguien + infinitive

Examples:

• Me cuesta hablar en público. = It’s hard for me to speak in public.
• Le cuesta concentrarse. = It’s hard for him/her to concentrate.

So here:

• me cuesta distinguir... = I find it hard to distinguish...

The infinitive works much like English to distinguish.

Because distinguir X de Y is a very common pattern in Spanish, meaning to tell X from Y or to distinguish X from Y.

So:

• distinguir la verdad de la mentira = to distinguish truth from falsehood / lies

This use of de is normal with distinguir.

You may also see distinguir entre X e Y, especially when talking about categories or options, but distinguir X de Y is especially natural here.

Examples:

• No sabe distinguir el bien del mal.
• Es difícil distinguir la realidad de la ficción.

So in this sentence, de is exactly what you would expect.

In Spanish, abstract nouns often take the definite article where English would often leave it out.

So Spanish says:

• la verdad = truth
• la mentira = lies / falsehood / the lie

Not because it means one specific truth and one specific lie, but because Spanish often treats these as concepts.

Other examples:

• La vida es corta. = Life is short.
• El amor es complicado. = Love is complicated.
• La paciencia es importante. = Patience is important.

So la verdad and la mentira sound completely natural here.

Because here la mentira is being used as an abstract concept: falsehood, lying, or what is not true.

So the contrast is:

• la verdad = truth
• la mentira = falsehood / lies as a general idea

Spanish often uses the singular for broad concepts like this.

If you said las mentiras, that would focus more on specific individual lies:

• Me cuesta distinguir la verdad de las mentiras.

That is possible, but it changes the nuance slightly. The original sounds more general and idiomatic.

They are very close, and in many contexts either can work.

• distinguir = to distinguish / tell apart
• diferenciar = to differentiate

In this sentence, distinguir sounds very natural because it fits the idea of telling one thing from another.

You could also say:

• A veces me cuesta diferenciar la verdad de la mentira.

That is understandable and natural too, though distinguir often feels slightly more common in this kind of contrast.

A useful breakdown is:

• A veces = sometimes
• me = for me / to me
• cuesta = is hard / costs effort
• distinguir = to distinguish
• la verdad = the truth
• de la mentira = from falsehood / from lies

So very literally:

• Sometimes, it is hard for me to distinguish the truth from falsehood.

That literal view helps explain why the grammar works the way it does.

Yes, a little.

The original:

• A veces me cuesta distinguir la verdad de la mentira.

is very natural.

You could also hear:

• Me cuesta a veces distinguir la verdad de la mentira.
• Distinguir la verdad de la mentira a veces me cuesta.

But the original is the clearest and most neutral.

Spanish allows some flexibility, but moving things around can make the sentence sound more emphatic, more literary, or less natural in everyday speech.

Yes, absolutely.

That means essentially the same thing:

• A veces me es difícil distinguir la verdad de la mentira.

This is a bit more formal or more explicitly descriptive.

Compare:

• Me cuesta distinguir... = very common, natural, conversational
• Me es difícil distinguir... = also correct, slightly more formal or careful

Both are good Spanish. The original with me cuesta is especially idiomatic in everyday use.

It can be either, depending on context.

It could mean literal difficulty deciding whether something is true or false.

But it can also sound broader or more philosophical, like:

• having trouble knowing what is real
• struggling to tell honesty from deception
• being unsure what to believe

That is one reason la verdad and la mentira work well here: they can express general concepts, not just one specific truth and one specific lie.