I think that human desire fools us into thinking that what we currently possess is not good enough and invites us to think that our neighbor has it better. By being happy and content where you are now is probably the best way to take full advantage of the moment and relish it for its true worth.
I have been guilty in my life of not following this principle but I am endeavoring more and more to change that. Realizing that where I am in life is a good place is the best way to lessen desire to be somewhere else.
This all relates to the idea of mindfulness which is not a new concept. Living in the present moment can save us an incredible amount of anguish as we take full advantage of the reality that the past cannot be changed and the future we stress about has not yet arrived.
I prefer to now focus on learning from past mistakes while not dwelling on them and using that past experience to craft a better way forward with a more positive spirit.