No pienso que + subjunctive

[fglorca]

“I don’t think that I will go to bed early until I’m tired.”

No pienso que me acueste temprano a menos que esté cansado.

Is it essential to use the subjunctive here after no pienso que, even though me acueste is in the first person singular?

Many thanks in advance.

[Rusty]

Yes, it is.
You can drop the 'que' and use the infinitive 'acostarme' if you'd rather, since there is no change in subject.

[AngelicaDeAlquezar]

I agree with Rusty. It's better to use the infinitive form, because for many native speakers the use of the subjunctive with the same subject is not just "clumsy", but incorrect.

[fglorca]

Thanks guys.
So, just to confirm, if I decide not to use the infinitive, and use "No pienso que me acueste" - is it true that this is grammatically correct, but not used very often?

Would the same apply to:
"Espero que apruebe mi examen." (I hope that I pass my exam.) I think this sounds grammatically incorrect? (Even though I would use "Espero aprobar..."

Thanks.

[Rusty]

If the subject is not changing, native speakers will use the infinitive.
In your second example, your listener will not hear "I hope I pass my exam." They will instead understand "I hope he/she passes his/her exam," unless you were NOT recently talking about another individual. If you weren't already talking about a third person, they would wonder why you didn't use the infinitive. It isn't grammatically wrong, but will be ambiguous for your listener.

[fglorca]

Thanks so much for your excellent explanations!