Religion and to some degree philosophy, may promote forgiveness. But how do you deal with: when people see that you forgive, that may give them a lesson that it is "ok" to do that to you.
Another thing is, the society doesn't tend to forgive: when your parking meter is over a minute or two, you can be given a ticket, and if you are able to find the parking patrol, a statement he is likely to give to you is, "over is over". To companies and coworkers, I don't think they forgive much at all, especially if it is a metropolitan, competitive city. A third thing is, if the society just forgive, there is no punishment, people may do whatever they want to do, knowing they would be forgiven and fearing no punishment at all.
But I did find that if I don't forgive, I feel quite bad, probably seeing so many bad things each day or each week and that I didn't forgive and let go.