We can use ‘wish’ and ‘if only’ to express wishes and regrets.

Wish/If only Structures

• I wish/If only + subject + past simple = to talk about things you’d like to be different now or in the future. Usually for very unlikely or impossible situations.
• I wish/If only + subject + past perfect = to talk about things that did happen in the past and you regret.
• I wish/If only + subject + would + infinitive = to talk about things that annoy us and we want them to change or stop. Don’t talk about yourself here, only other people.

Wish vs If only 

• They are both the same, only ‘if only’ adds more emphasis.