Having a rough day? Be content. Kids misbehaving? Be content. Somebody else got the promotion? Be content. Left out? Be content. Notice that in all of these situations you find yourself in...you are to be content. This means that because of the grace that has been shown to you through Jesus...you can be content in all circumstances.
Does this mean that we are to be satisfied and give up on dreams and getting that promotion or having a better day tomorrow? Absolutely not...it just means that you are content with what you have, but desire more for your life. Contentment is not meant to be used so that we "settle" for the way things are. Contentment is being okay no matter how things are, because you have a relationship with the One who made the Universe.
"The thief comes only to steal and kill and destroy; I have come that they may have life, and have it to the full." John 10:10 Don't let the thief (whether is it your wants and desires or selfishness) steal your joy or your contentment. Enjoy the life you have and live it to the full...be content.