Working out has become a regular routine for me since January and it does a body good.  I love the energy you get when you do a rigorous workout and the feeling you have in your muscles as they stretch and grow.  For a guy in his 40's I remember being lethargic all the time before I got on a workout regiment.  Now I have energy and can do things while working out I have not done since high school like chin ups and pull ups.  I reccommend as you get older to get off the couch and get out and walk at least to keep yourself active and keep the lethargic feelings at bay.