What if I did go to the party and the next day I say: How could I go? or How could I have gone?
Much obliged.
That would be rather odd. "How could I go?" doesn't work because the party has already happened. "How could I
have gone?" might work because it uses a past tense, and you are talking about yesterday. However, it only works if you are ashamed for having gone when you didn't mean to, or want to, go really. It expresses regret.
The only the only ways I can think of where that might happen is if either, someone put pressure on you to attend, for example, "If you don't go to that function you despise even though it's against your principles, then I won't approve your transfer/promotion.", or it might be more likely to happen if you were very drunk!
:drinking:
I suppose, it could also happen if it was an error of judgement on your part, which you later regretted. Perhaps you knew that an ex-partner, who you didn't want to see, might be there but you convinced yourself that everything would be all right, because you really wanted to go to the party. At the party, you met your ex-partner and had an argument, and so the next day you might tell yourself off with "How could I have gone?".
