Have you ever had a day where you worked steadily all day, with seemingly endless energy, and then once you stopped you feel like you were hit by a truck? I hate feeling drained like with, but I love knowing that I was able to get many things accomplished. Feeling drained from hard work should be rewarded with rest and relaxation.
Despite hating the worn out and tired feeling, knowing that you gave it your all is very rewarding. Being able to leave it all on the table (so to speak) and move on with the rest of your day is so healthy. Working hard for a little bit and then resting is key to avoiding burn out.
Burn out does not come as a result of hard work. Burn out comes from lack of rest and time to recharge after hard work. You have to allow yourself breathing room and time to unwind. Remember that hard work should always be balanced with something you enjoy.
Life is short, so work hard and play harder.