The services are hard. Fortunately I had my brothers there with me, and we shared good memories during the services. In the days and weeks following, I used that experience and took a few index cards and wrote some anecdotes and some of his favorite sayings on them so whenever I would feel bad I would read them and remember how much he had given me, so you might try that. Every case is different, in fact even different when my mom died a few months later, but it helped me to think of celebrating the life instead of dwelling on the loss.
I hope I'm not being too intrusive and I hope the advice helps out in a hard time.