I quit caffeine for like 4 months once, in the hopes of attaining the "increased natural energy" touted by some. All I really found was that I became less productive ... I'd find myself content to sit on the couch, doing nothing.
200-600mg caffeine everyday for me, keeps me moving around & getting stuff done. So yes, stimulants do improve my life.
Caffeine has many benefits to it and pretty much no negative side effects, why not use it?