Wish / If only

'Wish' or 'if only' is used to express a complaint, a wish, or a regret.

[1] Wish / if only + would + infinitive

It is used to show complaints about a situation; the speaker also expects a change in the future. For examples,
• I wish you wouldn't make the same mistake. [You usually make the same mistake.]
• I wish you wouldn’t drive so fast. [You drive too fast.]
• I wish my neighbors would not make so much noise.
• We wish our boss would give a pay rise.
[2] Wish / if only + past simple

It is used to show a state that a speaker is not satisfied with something presently and she wants to change it. For examples,

• I wish the room were colder. [The room is hot.]
• If only I was not fat, I would buy these clothes. [You are fat. The clothes do not fit you.]
• My computer broke down. If only I knew how to fix it!
• I hate traveling and traffic jam. If only I lived nearer the office.


[3] Wish / if only + past perfect simple

It is used to express regret about past actions (the speaker wants to change the past). For examples,

• I wish I hadn't drink so much. [I drank a lot then.]
• If only I had studied hard, I would have passed the exams. [I didn't study hard, and I failed in the exams.]
• We wish we had attended the meeting.
• We got wet. I wish we had brought the umbrella.

NOTE: Wish + to do something = means "would like/ want"; for example, 

• I wish to finish the assignment today. = I would like /want to finish the assignment today.