I would like to chime in that I also very much enjoy L-Theanine. In addition to (I think) helping me focus, it has an even more pronounced effect on anxiety. When I take L-Theanine and have some obtrusive thought -- cooked up especially to make me anxious by some adversarial force deep in my sub conscious -- I can pretty easily let it go. Most noticeably, the strong 'pit in the stomach' feeling that both signals and reinforces anxiety is absent.

I would encourage nearly anyone to try it. It's an amino acid found in the highest concentrations in green tea. If you've ever had a couple cups of green tea and noticed you feel relaxed and focused, you might want to try an L-Theanine supplement.