"To była moja wina."

Translation: It was my fault.

[Zkamin]

To były moje wina: Those were my wines. Dlatego tak ważne jest, aby poprawnie odmieniać.

[JamesTWils]

So, is była meant to agree with wina, rather than to?

[immery]

Yes, it happens only with to=this/those.

[Stefan873422]

What would be 'this was my wine'? To było moje wino?

[Jellei]

Yes, exactly :)

[Popo-lsku]

Now i am a bit confused!?
"To byłA mojA winA." has to do with the gender (female) of the speaker!?
But what would it be for a male speaker? "To był mój...(?) winy???

[JamesTWils]

No, the verb and possessive pronoun are only feminine because the noun (wina) is feminine. The speaker's gender only has an effect if he or she is talking about himself or herself.