Read the tired student's text message and choose the correct phrase to complete it.

I'm so exhausted today. If only I _______ to bed earlier instead of watching three hours of skateboarding cats.

The correct answer is had gone.

We use if only + past perfect (had + past participle) to talk about things we would like to change about the past. The student didn't go to bed early, so the contrary-to-fact past wish is "had gone."