Effort

 A principle that I have come to accept is "work smarter, not harder". I have learned that putting in a lot of effort to accomplish and goal that you'll have been attained with a far less amount of effort is very ineffective. Sometimes I will invest energy in people and think, "well, if I put in this effort I will be rewarded" when knowing the result will be poor before entering the interaction. I go through life surrounded by so many people that I've realized it's foolhardy to not be smart around them.