Tea does have caffeine, but doesn't necessarily keep you awake. If you have four cups right before bed, yes. Drank throughout the day, it can help you relax:
BAM!I'm a total caffeine addict, so I have a very high tolerance, even able to drink a cup of coffee before going to sleep. I avoid energy drinks and stuff, as it turns out those can turn me into my patients.
Also you are what you think. In essence; and this is backed up by neurology: "The neurons that fire together, wire together."
That is the more you go with your everyday reactions to things, the more those reactions become hard-wired into your brain. For example, I used to become annoyed at every red light. Left unchecked, that type of reaction can eventually have a simple red light turn you into the rampaging Hulk.
Taking a moment and stopping yourself, and trying to think positively. (Ah, an opportunity to adjust my mirrors, this is perfect.) or even forcing yourself to smile can rewire those neurons. If you force your smile, its disingenuous at first, but eventually the areas of the brain associated with it kick in, and your producing happy hormones instead of angry ones.
So it's sort of meditation, sort of just being aware of what you're thinking. Just a thought.