For me, most people I meet day to day, they don't even exist past our minor interactions, most of which are positive because I'm positive.
The few folks who I interact with on a regular basis - it is all positive, or else I'd stop interacting with them.
There are situations where you have to regularly interact with people who are going to be annoying (teachers in school, parents if you live at home, boss at work, etc) - you just have to learn self-defense tactics and work toward being more independent.
The people who are annoying - they are just incompetent at life. Their life sucks with me in it and with me not in it. The rest are either not affected or affected in a positive way.
So I don't know where you're at but if you're not a net positive to those around you - you have got some work to do.
The reason some people are mopes is as I mentioned in the last post - they just are. They're stuck. Don't get stuck wasting your time being 'positive' to them.
Be positive to yourself by not spending time around people who make you feel like shit and spending time around people you can learn from instead.
Easier said than done of course, one step at a time :)