I relax through working only. I never get tired of working. In fact the opposite tires me. If you have to write 10 letters and you may start feeling tired after writing two. But you feel satisfied if you have finished writing all 10 letters and skipped your meal because you feel the work is finished. Actually we get tired by not working and work gives you satisfaction. That satisfaction gives you energy. I have felt this and always tell this to my young friends. Tiredness is more psychological. Everyone has the same capacity needed for the volume of the work. You keep accepting new challenges and your inner self will always back you. This is in-built.