I find it better to let go after a while. Life’s just way too short to continue to hold a grudge, plus it could most likely affect my blood pressure.
I won’t necessarily forgive, mind you. If someone (or in the case of current politics) some figure or organization, does something that affects me (or a large portion of the population) in a damaging way, and I know that what happened was not my own fault, then I can’t forgive. I also don’t forget. In the case of politics, there is the option to get rid of the one who damaged a society by voting them out of office. On the other hand, at the more local level, when it’s just between two people especially if they see each other a good deal of the time, it’s a little more difficult. I won’t hold a grudge, but I necessarily won’t forgive either.