Si yo hubiera sido más paciente conmigo mismo, habría evitado mucha ansiedad.

This is a past unreal (third) conditional, the same type as English “If I had been more patient with myself, I would have avoided a lot of anxiety.”

It expresses:

• A hypothetical situation in the past that did not happen (I was not more patient).
• A hypothetical past result that also did not happen (I did not avoid the anxiety).
• Usually a feeling of regret, reflection, or self‑criticism about the past.

Because the clause with si talks about an unreal / contrary-to-fact past situation.

• “hubiera sido” is the pluperfect (past perfect) subjunctive of ser.
• In Spanish, when you say “If I had been X (but I wasn’t)” about the past, you normally use:
  • si + pluperfect subjunctive → “Si (yo) hubiera sido…”
  • and then a conditional perfect in the result: “habría evitado…”

Using “si fui” or “si era” would sound like you’re talking about a real situation in the past, not an unreal one:

• Si fui más paciente, evité ansiedad. → If I was more patient (and I actually was), I avoided anxiety.
  (Different meaning.)

“Hubiera sido” is the pluperfect (past perfect) subjunctive of ser.

Formation:

• Take the imperfect subjunctive of haber → hubiera / hubieses / hubiera / hubiéramos / hubieran
• Add the past participle of the main verb.

So:

• haber (imperfect subjunctive) → hubiera
• ser (past participle) → sido
• → hubiera sido = had been (in a hypothetical / subjunctive sense)

“Habría evitado” is the conditional perfect of evitar.

Formation:

• conditional of haber → habría
• past participle of evitar → evitado
• → habría evitado = would have avoided

In past unreal conditionals, Spanish typically uses:

• Si + pluperfect subjunctive → Si yo hubiera sido…
• conditional perfect in the result → habría evitado…

You can also hear:

• Si yo hubiera sido más paciente, hubiera evitado mucha ansiedad.
  (Pluperfect subjunctive in both parts; also common and accepted.)

Because ser is used for more permanent or characteristic qualities, and estar for states or conditions, especially temporary ones.

• ser paciente = to be a patient person / to have patience as a trait or behavior.
• estar paciente sounds odd; patience is usually not treated as a momentary physical state.

So:

• hubiera sido más paciente = had been more patient (as a way of acting / as a quality)
  That’s the natural way to say this.

Using “hubiera estado más paciente” is grammatically possible but sounds unnatural or off to most native speakers in this context.

You can absolutely drop “yo”, and that’s actually more typical in natural Spanish:

• Si hubiera sido más paciente conmigo mismo, habría evitado mucha ansiedad.

In Spanish, subject pronouns (yo, tú, él, etc.) are often omitted because the verb ending already shows the subject.
Here, hubiera and habría both point to “yo”.

You would keep “yo” if you want to:

• Emphasize contrast: Si yo hubiera sido más paciente (and not someone else)…
• Be very clear in a context where it might be ambiguous.

• conmigo = with me
• conmigo mismo = with myself (emphasizing that you are treating yourself in a certain way)
• a mí mismo = to myself (different preposition and slightly different nuance)

In this sentence, “ser paciente conmigo mismo” means:

• to be patient with myself
• It’s about the attitude you have toward yourself.

You could also say:

• Si hubiera sido más paciente conmigo, habría evitado mucha ansiedad.
  → understandable and acceptable, but “conmigo mismo” is more explicit and sounds more natural when you mean “with myself” rather than just “with me” in a physical sense.

“A mí mismo” is more like:

• decirme la verdad a mí mismo = to tell the truth to myself
• not the most natural choice with paciente, where the preposition is normally con.

Yes.

The word “mismo/misma/mismos/mismas” agrees in gender and number with the person it refers to:

• Man speaking:
  Si yo hubiera sido más paciente conmigo mismo…
• Woman speaking:
  Si yo hubiera sido más paciente conmigo misma…
• Group of men / mixed group:
  …con nosotros mismos
• Group of women:
  …con nosotras mismas

So a female speaker would normally say “conmigo misma”.

Because “ansiedad” is a feminine noun in Spanish: la ansiedad.

Adjectives and quantifiers (like mucho/mucha) agree in gender and number with the noun:

• mucha ansiedad → a lot of anxiety
• poca ansiedad → little anxiety
• tanta ansiedad → so much anxiety

If the noun were masculine, you’d use mucho:

• mucho estrés (masculine: el estrés)

No, that would be incorrect or, at best, sound very wrong.

In Spanish:

• Quantity words like mucho/mucha normally go before the noun:
  • mucha ansiedad
  • poco tiempo
• Regular descriptive adjectives usually go after the noun:
  • ansiedad extrema
  • tiempo suficiente

So the natural order here is:

• mucha ansiedad, not ansiedad mucha and definitely not ansiedad mucha evitado or similar.

Yes. That’s a more formal or literary structure, but it’s correct and natural:

• De haber sido más paciente conmigo mismo, habría evitado mucha ansiedad.

This is similar to English “Had I been more patient with myself, I would have avoided…” (dropping “if”).

So, you have:

• Neutral/common:
  Si hubiera sido más paciente conmigo mismo, habría evitado mucha ansiedad.
• More formal:
  De haber sido más paciente conmigo mismo, habría evitado mucha ansiedad.

Both mean the same.

Yes, a very natural alternative in Latin American Spanish would be to use “ahorrarse”:

• Si yo hubiera sido más paciente conmigo mismo, me habría ahorrado mucha ansiedad.

Here:

• me habría ahorrado = I would have saved myself / spared myself (a lot of anxiety)
• This sounds very idiomatic in everyday speech, while still being correct and clear.