Constantly focusing on the next best thing creates unhappiness. We start to criticize ourselves and possessions. We compare ourselves to others. It creates discontent in our current life. If these thoughts start to get out of control, we start to lose sight of what can make us happy each and every day. Finding joy in what we do have creates contentment. It cultivates an attitude of gratitude. I read the following quote by Epictetus and thought it was a good analogy for how to look at life and reduce wanting.
I try to remind myself of this quote when I find I am being critical of my situation. That finding contentment eludes us when we are always looking for something else instead of focusing on what we currently have and being thankful. Your situation could always be "better" if you are always focusing on what you don't have in life. I am not saying that if there is something that you want to not set goals and strive for it, but to be thankful for where you are in your journey. Take time to appreciate how far you've come. Enjoy the journey.