If only expresses a wish—one that you are doubtful about actually happening. (=OJALÁ...)
The result clause is optional and it is written in a new sentence.
If only I had more time!.... I could relax.
If only you would clean up your room. You would find your lost jeans.
If only I had some Zing window cleaner.
If only I could please my mother-in-law.
If only you were here!
If only he hadn't told his mother everything.