Do your best to maximize your energy levels all the time, to the best of your ability, no matter what. This should be a perpetual goal that you have, that never ends.

Everything makes sense when you have high energy. 

Everything feels pointless, meaningless, and hopeless when you have low energy.

How big your goals are, whether they are short-term or long-term goals, is contingent upon your energy at the time of coming up with them, and at the time of execution.