Forgiveness is hard to do for a lot of people, for many reasons.

All through our lives we're conditioned to feel guilt in some form, whether it's letting parents down with school grades or ourselves with our behaviours or reactions, we don't forgive ourselves and guilt then forms and we start a vicious circle which then makes it harder to forgive etc etc 
When we begin to forgive, the ideal place is to start with ourselves, maybe we don't live upto other's or our own expectations, and it's fine. 
When we think back over situations or events that we hold in and numb our emotions to, the best way we can look is, did we have any control over events? maybe we were children or someone else made us feel inferior with our decision making?  Maybe we made the right choice at the time or a decision that was the only choice we had at that time?  Many different factors come into our minds as we think, hindsight is a wonderful thing and hindsight can help you with forgiving yourself. Maybe we don't like who we are as a person or some of our traits, usually we can look back at parents and see ourselves in them, sometimes the parts of our parents we disliked or try to not be can be the part of us we don't like and that can be a thin line. 
When we broaden our thinking and try to understand why things happen or maybe why people are how they are, maybe because of their learnt behaviour, we start to see patterns we can break or change, this is when you can start to forgive yourself, situations, choices etc and you will find acceptance is a part of forgiveness too. In time you may be able to forgive more than yourself