First off, bummer dude. Good luck with the time you have left.
The only big lesson I ever instilled in my daughter, and I think it stuck, is that everything in life that you want has a cost. It may not be money - in lots of cases it isn't (my daughter's Field Hockey championships and ROTC scholarship for instance) - but there is a cost to everything. Figure out what the cost is, and if you want whatever it is enough to pay that cost - do that, and life is simple.
The other I got from someone else - at some point EVERYONE becomes an orphan. When you can understand and accept that, you at least know you are not alone in your loss - sooner or later everyone has it.
Good luck - god bless