This is late and perhaps somewhat aside from the gist of the discussion right now, but most sources I have sought suggest that most of us should not be taking more than 3mg of melatonin if taken each night. I have trouble sleeping at times, usually long enough. The quality is quite decent, but I awaken near the 5.5 hour point and that's usually 'it' for me. So, I take a single tablet of 3mg of melatonin, but only every third or fourth night. This way, its effect does not become reduced due to habituation or to adaptation, and its effect is more potent on the nights I do take it. Even so, there are more potent pills on the market, and the general consensus I have found is that it is too much. Additionally, although I haven't felt the need to use it in some months now, after my angiograms and two ablations for atrial fibrillation, I had difficulty falling asleep. I asked my physician for help, and he prescribed zopiclone at 7.5 mg. On the advice of my pharmacist, who knew I have sleep apnea, I only took half a breakable tablet, and that worked very well.
It may just be my upbringing and/or personality, not to mention my phenotype, but I find that if I tough it out for a few days, and then take the 'help', that I usually, not always, get a good night's sleep that way. It's as if my mind calms knowing I have gotten some assistance and I usually sleep longer that night.
One last message from me, and again it might be my thinking only on this matter: I don't like having to take medicine at all, but I don't have other answers when it comes to intractable and serious conditions. If you need the help, especially just for a night or two to get past a tough patch, then go ahead, and don't look back. It just builds more angst, self-recrimination, and sets limits on what the medicine can do for you. Fighting the need only goes so far, and in the end, you ARE doing it for your health!!