You have to keep track of these grievances though, otherwise you might be naturally happy with all your blessings ... or you might treat someone nice that
1st Corinthians chapter 13 talks extensively about Charity. Perhaps I will commit it to memory so I can share it more freely with those around me who seem to always find (or remember) grievances they have against other people. Verse 4 reads: "Charity suffereth long, and is kind; charity envieth not; charity vaunteth not itself, is not puffed up," and verse 5 continues "Doth not behave itself unseemly, seeketh not her own, is not easily provoked, thinketh no evil;" Those last two thoughts summarize the message I wish these people I know would recognize and apply to their lives.
I suppose it is a good thing that I am usually quick to forget things because it allows me to be unburdened by carrying all these grudges against all these people in my life. Ultimately, they are really good people and almost guaranteed if they offended me it was completely unintentional. I've only known two people in my life who were actually trying to offend me or cause me pain ... and I do not associate with either of them any more so that problem is solved (for me anyway ... for them I hope they find some help to overcome that bitterness).
I believe these individuals who are quick to anger against others likely have a deep down hurt which probably stems from a low self esteem. If that is you and you are reading these words, please remember that you are a Child of God and your Father in Heaven will always love you. You can do great things and be a great person even if you're imperfect (like the rest of us). Just start with some simple charitable act towards anyone in your life and bask in the great feelings you will have from ignoring your needs just for a minute and focusing on others. I know you can do it!