Stopping having caffeine has been one of my best decisions in terms of health, energy and especially mood.
Caffeine is like a double-edged sword, it does make your mind sharper and gives you a boost of energy....but then you crash and you're worse off, feel even more crap and then need more.
I find it best to try keep my sugar levels level which gives a more steady, constant amount of energy without any spikes and crashes.
I just replaced the habbit of sipping a mug of a warm drink while watching TV or on computer with something else, I now drink rooibos tea which is naturally caffeine free. There are also quite a few naturally caffeine free coffee's made from rye, barley etc.
I've reduced decaf, since like regular coffee it is quite acidic, possibly even more due to the process to get rid of the caffeine.