Years ago I attended a day-long meditation class (part of the childbirth class I was taking), and one of the things we did was lovingkindness meditation.  I find it very helpful for dealing with stress and stressful people.

Here’s how you do it:  first, find a quiet place to sit where you won’t be interrupted.  Then you traditionally use four people to focus on; first yourself, then a loved one (a pet, your baby, your S.O., etc), then a neutral person (someone you don’t know well, like a supermarket checker or the mail carrier, or someone at work), then a difficult person (start with an easy difficult person…), then all living things. 

For each of these, you repeat these phrases (out loud or to yourself), or something similar that works for you: 
    May I be safe and free from harm. 
    May I be healthy.
    May I be truly happy.    
    May I love myself unconditionally.      


For the other people, visualize them in front of you, and say the phases to them. Start with someone close, then someone neutral, then a difficult person:
    May you be safe and free from harm.
    May you be healthy.
    May you be truly happy.
    May you love yourself unconditionally.  


For all beings, reach out to the world and say this:
    May all beings be safe and free from harm.
    May all beings be healthy.
    May all beings be truly happy.
    May all beings love themselves unconditionally.  


Here are some other versions with more instructions:
http://www.beliefnet.com/Health/2000/07/Opening-The-Heart.aspx 
https://soundcloud.com/insightla_meditation/36-minute-guided-lovingkindness-metta-meditation-with-trudy-goodman

One thing to remember is that you can only start from where you are, so don’t worry if it feels fake or uncomfortable, or if you can’t imagine these things being true.  This is about setting an intention for what you would like to happen.