Writing a letter to my unborn son

I've started writing a letter (more of a guide) to my son. I want it to have my take on certain things, as well as guidance about how I did things wrong, and how he should try to do them better. It's sort of a 'book of the five rings' without the poetic feeling. I don't know exactly what will be in it,  I'm just sort of typing it when I feel motivated. It's very stream of consciousness.

I know these sorts of things are done when the parent is terminal w/ some disease and they want to leave a record for their child. I'm not planning on checking out any time soon. This is a 'just in case'. Plus, it's a great exercise for myself. It's a real challenge to think about how you think. Why you think it.

It's also hard to not sound self-righteous when writing something like this. I'll try to make it as true and honest as possible.