Happiness is a choice. You can make the decision to look for the good and to be happy, no matter how your day goes or how you are treated. 80% of your experience is up to you. Yes, not everyone is a nice person out there and things happen that aren't great but you can decide to flip things to the positive no matter what happens.
It's always a wonderful bonus when people are nice, when people do their job, when things click, but I have learned that more often than not, this is not the case so it is important to find the good, the positive. It's important to treat people with respect and to be nice no matter what. Search for the lesson. Search for what you can learn. Work hard to be the best you can be every single day.
One of the best books I have read to help me understand this was the NY Times bestseller by Peggy McColl, YOUR DESTINY SWITCH. Find it on amazon.com or barnesandnoble.com.
Another great book out there to read is YOU CAN BE HAPPY NO MATTER WHAT by Richard Carlson, Ph.D.