Son...No expectations!

I have often thought of writing a letter to my son but I've never really made up my mind. Not because I don't want to but I fear that 18 something years down the line, I might chance upon the letter again and find that I have broken most promises I made in the letter (just like when I was pregnant). Or worse, that he will never see the time and energy I spent writing to him and the point I try to convey might be forever lost. I envision all sorts of things and that's why I will never have the nerve to begin one. There's nothing wrong about having dreams for a child (in fact, everyday I dream of what he will accomplish in his life) or envision the future our kids will live (and with the speed the world is moving, who knows how that's going to be). But as we all know, parenting does involve mistakes and some promises will be broken, so with that in mind, I do not want to set any expectations on what advice I think (or assume) he will need.
For a start, what if I give him advice on marriage and everything that comes with it and then he decides he does not want to take that path. Would I be shattered? Of course, because here I am writing him a letter advising him about what he should know  about marriage and many years later he will see that at 1, I was already vigorously planning years ahead for his future. Or take for instance the promise I make never to stop him from realising his dreams and he decides to take some drastic path that will scare the life out of me and is bound to have me objecting to it. No, I don't want to do all that. It's easier to make promises and stuff now, when he's so tiny and realise later 'what the heck was I thinking' (and that much scary if I have put it on paper). Instead, I wish to go with everything that happens and ensure I teach him well (save all that advice for when he's older) and also be prepared with the toughest armour (lest he decide something out of the ordinary). My hope is that I will be lucky enough to be there with him to celebrate his victories, share in his disappointments, and offer advice (maybe not always) all without having any expectations of what his future holds.