I too was like you and still am a bit. very sensitive and took things personally. with time being on the job as a nurse and just growing a bit more mature I realized other people's negativity isnt worth my energy ( now of course is someone is harrasing you that is different and calls for management involvement) but when a co worker snaps at me, a md gets *****, or a pt is being difficult I just dont react to it and i brush it off. I have a natural happy disposition and I have spent way too long of my life/nursing career letting other's people negative attitudes affect me so I dont let it anymore. I kill my difficult pts w/ kindness ( works 95% of the time, most people cant be ***** for long enough towards a nurse listening with interest and being kind and if it doesnt they cant say I was rude!) with my md's I dont even get them a second thought if they are having a moment unless its something I can learn from, and with my co workers most of the time the snips are when we are all under pressure and I have done it myself too so I think we all have a mutual understand that we all might get snippy sometimes and to not take it personally.
And I agree with pick your battles. If I am really offended or feel I have been treat un fairly I rate it on a scale of 1 to 10. If its a 1 through 7 usually its not worth my time to do anything about but if its a 8-10 I take action and its always worked well in my favor. Most of the times its a hey look I didnt appreciate XYZ, if you feel like I am doing something thats not working for you could you just discuss it with me in a appropriate time and manner and we can go from there? I think a lot of times people just dont realize how they come off and if you approach them in a calm/confident manner it can usually get resolved.