That if at first you don't succeed, try and try again. However if you fail to succeed within a few years then perhaps you need to overhaul your approach/mentality, you may even need to look yourself in the eye and ask why you're not achieving and whether you're deliberately chasing something you know you're going to fail in to avoid the uncertainty of actually having to go forward with whatever it is you were trying for.
Never trust an addict with money, or to be precise be a kind relative and do not provide someone with a fragile/obsessive personality the chance to be tempted. Also that at their worst an addict will sell everything they hold dear for the smallest morsel of what they crave.
Remember that everyone is human and even those prized above all others for their selfless works had days of selfishness. Remember that people lie, and not always for the reasons you think.
If you want to keep a secret, don't tell anyone. Not even your closest friend. Everyone has someone they confide in, and it's not always the person that confides in them.
Treat others as you wish to be treated. Don't just say it, live it.
Not everyone is destined to make a name for themselves, to be known, to have a job deemed "valuable" in the world; and that's OK. The only thing that is important in life is that you make it your own. No sighing, no wishing, make it into something that lets you get what you want.
Don't trust that first rush of "love". It's not love, however deep you may believe it to be. Love comes after that intense rush, after the proclamations of never having felt this way about anyone else. It's the undercurrent, the fainter bits that will keep the relationship alive because you actually like each other. Love and like do not necessarily go hand in hand.
Fashion is not what someone else tells you, it's what you make for yourself. Wear it, own it.
Everyone believes in something, even if what they believe in is nothing at all.