Get over it.

I find my thoughts wondering off the most when I'm having my exams - I must be in denial.

Perhaps every now and then, someone will have to tell him/her self to get over it. Decide to get over it. But there are a myriad of things that people don't get over - then how?

Perhaps we don't have to get over them things. Mayhaps all we have to do is to remember them; for the good and the bad.
Remember the lessons learnt by reminding your good self about the pain and suffering you experienced so that you won't commit a mistake like that ever again - you try.
Remember also the joys during better times so that when you inadvertantly indulge yourself again in future, you comfort yourself that at least it was good while it lasted - only for a while.

Just don't dwell on it.
Get over it.