I would forgive them but I never really blamed them to begin with. Any amount of bullying I got, which wasn't a lot but others may beg to differ, wasn't a malicious attack on me purely to hurt me and mess me up. Most bullying is done by kids; high school, middle school, grade school. Younger kids especially are extremely egocentric, and don't realize that what makes them feel better by raising their self-esteem and helping them fit in with their peer groups is hurting the person they need to belittle to get there. That's why years later some may act friendly and not realize they had a negative effect on your childhood, they simply didn't realize they were doing anything hurtful.
And for those that do, bullies more often then not have their own slew of problems, which is why standing up to them makes them stop often times. They are usually bullied themselves, or have a bad home life or have some reason on need to bully. Even just the pressures of school is a driving force of bullying, with it being such a judgmental and dog-eat-dog atmosphere. They are small people, with self-esteem even smaller. They feel they need to put others lower than themselves to hold a status of authority, because otherwise they'll lose it. Someone with good self-esteem wouldn't worry about that or feel the need to bully, unless they are just straight up mean and malicious but honestly I think that's not the case most of the time.