http://ask.slashdot.org/story/15/02/25/1636259/ask-slashdot-terminally-ill—what-wisdom-should-i-pass-on-to-my-geek-daughter

I would want my daughter to know the following:
1) I work am a child psychologist and interview parents all the time. When I ask what they want for their child, I am always happy to hear something along the lines of happy and independent when they reach adulthood. Make sure she knows that you goals for her are generalized to her happiness and independence, not specific things such as attend Notre Dame and become an accomplished engineer.
2) Know that she is loved for who she is. (especially by you and her mom) Know that other people do judge you and it can be harsh, but one of the awesome things in life, is that as you get older and are better able to choose the people with whom you interact, the fear of this judgment decreases. The “It gets better campaign” for LGBT youth is a founded on this concept, but I think it applies to all teens.
3) Girls are unfairly subject to society-specific, irrational concepts like having to look a certain way or behave in more rigid patterns. She does not have to follow those patterns unless she wants to.
4) Guys, especially in high school and college, heck many adults, can be driven by hormonally-driven motives. Watch out for hormones combined with lousy environmental circumstances like alcohol, drugs, dark alleys. Guys in high school and college also have immature pre-frontal cortices, resulting in increased impulsiveness. Make sure she has a solid set of friends that help watch out for one another.
5) The world is a fascinating place, go see it with an open mind and find new ideas that make your part of the world better.
6) The meaning of life is elusive, but to some degree we get to define our own. I have chosen that I want to make the world easier and better for other people as my meaning. I am doing so and therefore everything else is usually pretty cool. Make sure she knows to seek meaning in things that she can have control over. Psychologists refer to this as increasing your perception of self-efficacy, which usually correlates with increased optimism and happiness. This will be particularly hard in the face of the uncontrollable circumstances that led to why you are recording these things for her.
7) Record some of the goofy, stupid crap that you loved about your life, and some of the stuff you wish you would have avoided. New details from your life will help her feel close to you even after you are gone.
8) Make sure she knows that she can grieve and that it sucks and it is not fair, and that you feel the same way. Make sure she also knows that if she has a hard time grieving, that it is totally cool with you if she seeks help to figure out all the complex feelings.
9) Let her know that it is okay for her to be happy again. So many people grieving for loved ones feel bad when they feel happy, or feel like they “forgot to be sad”. As though they are not doing due diligence to continue being sad over the loss. Making sure she has active access to enjoyable activities and social support. She might feel like she is “forgetting you,” but reassure her that you know better. All you would want is for to be able to really enjoy the life she has. Having room in her head for all of the great times your family shared is part of that, but so is her capacity for building new great memories and experiences, and that is not a betrayal to you.
10) I would leave some pictures of prized possessions and experiences, with an explanation of why they are prized. Again, this will let her continue to get to know you.
11) Writing about complex ideas helps us understand and let go of negative feelings associated with things such as death or trauma. I would encourage her to keep a journal, and if comfortable doing so, share it with her mother to help figure these things out. It is a lot easier to recognize incomplete or irrational thoughts when we write them out.
Sincerest wishes for the least painful end possible