Wish and ‘If only’ are both used to talk about regrets – things that we would like to change either about the past or the present.
Talking about the present
When we talk about present regrets, both wish and if only are followed by the past simple tense. The past tense emphasises that we are talking about something ‘unreal’.
Talking about the past
Both wish and if only are followed by the past perfect tense when we talk about past regrets.
Wish/if only and would
We use wish + would to talk about something in the present that we would like to change – usually something that we find annoying.
NB We can only use wish + would to talk about things we can’t change.
I wish I wouldn’t eat so much chocolate is not possible although we can say I wish I didn’t eat so much chocolate