If you read the Bulbapedia page, you should already have the answers to your question.
It'll disappear after you use it, and has absolutely no use in battle, so it's basically just a one use move that's like a pat on the shoulder. If you're not using the Pokemon for any competitive battling, then sure keep it for a 'special' occasion. If you are going to battle with the Pokemon, just use the move in battle ASAP.
Instead of drowning your misfortunes in a hand held game console, perhaps it would be wiser to either find new friends or tell people something important is coming up; one has to realise that no one remembers everything.