As I wrote about in The 5AM Club, everyone alive does the best that they can based on where they're at in terms of their awareness and their understanding of life. And once you realize that, you won't be upset with them - you can begin to forgive them.

So resolve to forgive those who have hurt you [they made you stronger and more noble]. And commit to letting go of what no longer serves you [it got you to here]. Remember that the past was perfect preparation for you to become who you now are and to grow the extraordinary life that you now face the opportunity to create.