Throughout the day I take few moments to take a dep breath and just be happy, even if everything is shitty for me at the moment I'm just happy that things aren't shittier and If things are too bad for that I'm just happy that someone somewhere is happy. It sounds stupid but I really like this outook that HPPD has given me.
Dont let little things get to you. Most of the things that bother people shouldn't, who cares if the person in front of you in the check out line is taking forever, getting upset about it isn't beneficial in any way to anyone.
Don't get mad at people. Give people the benefit of the doubt even if you hate them sometimes. Lots of people do asshole things (I feel like shit cause I was a complete jerk the other night) but few do those things to purposefully hurt you. Most do it because they are driven by material objects, try to get satisfaction from other more important things. I'm not trying to say you should give up all of your possesions, just realize that they aren't what's most important. When I near death I don't want to have any regrets about wronging anyone in order to get what I wanted.