Anger and Forgiveness

Forgiveness is sort of a touchy subject sometimes. I myself have easily forgiven lots of things but not so easily forgotten them. Because of my lack of forgetfulness, I often wonder if I really forgave to start with!!
In my heart of hearts, I do know that I truly hold no grudges for things from my past at this point in my life, and realize that at no time during most of those occurrances, was I completely innocent. I say that because although some pretty messed up things happened to me in the past, I may have allowed myself to be a part of it by not breaking away from the relationship and standing up for myself, or I may have gossiped about situations after being disappointed and hurt by someone, or may be I didn't handle it all in the best manner. The truth is that no one is perfect, and we all make mistakes, whether big or small.
I'm able to consciously look back on things to place where somewone went wrong, why they may have done such a thing, and what I could've done differently. My problem arises when someone doesn't acknowledge they've done any wrong, and doesn't feel any need to change... Sort of continues down the same path without caring whose lives they affect. I'm not really sure how to deal with that- it something that upsets me- kind of makes my normal good attitude turn sour. It makes it hard for me to continue relationships or be around the people who behave in these ways. It doesn't even have to be someone I have any real relationship with- for example, a student comes to school daily late, and is tired all the time (so much that he/she cannot focus on his/her studies). His/her clothes are alway dirty and hair is never brushed...he/she may or may not have had a bath in several days. I get angry at the parent who when spoken with about the matter always has an excuse. In my mind, I'll never understand that. There are so many parents that just put themselves before their children, and some of them don't even realize that they do it! It's maddening, really.
I'll also never understand jealousy of having certain things, when for the most part, we all have opportunities to make something of ourselves. I bet it's difficult to find someone successful just -in general life- who doesn't have some sad misfortune in their past that could've held them back- but they didn't allow it to. I know we all have some moments where we wish we had something someone else has, or we wish we could do something that someone else is doing, but I'm talking about feeling sorry for yourself and being irritated with that person- like it's their fault you are where you are. It's ridiculous, and it also makes me angry, lol!
The truth is to truly forgive is to completely let go of something, to have a heart like Christ and love people the way he does. If only it were that simple, right?! It's pretty black and white though- there aren't any gray areas, although we like to create some. It always sounds good when we rationalize with ourselves or others around us- but that doesn't mean it's ok.
I am relieved at this point in my life, that I don't hold any unforgiven circumstances in my heart. I have really forgiven those who have wronged me, and hope that I have also been forgiven of the wrongs I have done. My true issue is what I spoke of above, just random, every day things people do (or continuously do) without thought or with selfish thought. That is where I need the most work. I know it's ok for me to be angry for injustices, but holding on to those angers and having a bad attitude- not so ok.
I'm going to figure out a way to work this out, even if it is just memorizing a verse to say every time I begin to feel that way!