How do I become a good person?

I'm not trying to make exuses but life has been tough for me. There are some big things in my personal life that messed me up and I start to realise I take my frustrations out on people.

I don't hit or punch anyone thankfully but I get pissed off really fast and I curse at people, talk bad about people behind their back and I just feel like my additude has been bad. Just like today I talked shit about my college with a friend not realising she was close by this kind of made me realise I really need to change. Does anyone have advice I could use it :,)