Some random thoughts from someone who's working through the same thing (though not with a straight friend, I just don't get that

).
Don't pretend your feelings don't exist, but don't indulge in fantasies: keep telling yourself what the reality is
Don't pointlessly distract yourself, but make yourself focus on what needs doing or what you want to do
To do that, some kind of meditation technique (I just use a mental: breathe in, breathe out) helps with the low-level stress and the intruding thoughts
I would feel much, much worse if I didn't have friends I can talk to about this
The friend who I'm getting over recommended a book to me (not in order to help me get over him

) called 'Who moved my cheese'. It's a simple little self-help book which is meant to help kick-start you into accepting unavoidable change. One key message from the book is:
The quicker you let go of old cheese, the sooner you can enjoy new cheese.
Another is that the process of searching for new cheese can itself feel good, because you're controlling your situation and moving forwards.
Ìf you find yourself unwilling or unable to search for new cheese, ask yourself why and work on that.
I hope all that helps, because if it doesn't, I'm not doing the right things!