I am of the opinion that you can only go forward, though that is just my refusing to accept any possibility that someone could go back and change the past at any moment, thereby taking any semblance of control I have over my life away. You can only alter the ever-changing future, not the brick wall of the past.
Of course, that's just me.
EDIT: I don't think forwards is a word. If it is, I feel stupid. If it isn't, I feel stupid for putting it in this entry before this edit was made.