What you do today will affect others tomorrow. Make the best decision you can with the information you have.
The most difficult thing in life is to get started; to act upon your desires. After that, it's your tenacity and persistence that will carry you forward. Passion and drive wax and wane; they fade in and fade out. But tenacity, stubbornness and persistence can carry you through those times when your passion dips. If it's something that you truly want, unleash your persistence and tenacity.
Long days at work aren't just physically draining, they can be emotionally draining as well. It's important to maintain your physical health, but it's also important to build your psychological stamina.