I suffer from ADD/depression, which always means trying to strike a delicate balance between hyper- and hypo-excitability; in all honesty, I would rather be anxious than apathetic because at least it means I can get some stuff done. I've been having a lot of trouble sleeping and decided to try Beta-Alanine, which I used to find helpful. I am calmer today, but completely lethargic and depressed, with no interest in anything. I used to have trouble with glycine too, even though I slept so deeply on it. Is it possible some tolerance can develop to these effects, particular if my receptors are initially more sensitized?