I'd first make sure that I had a way to end my life, at the time I choose, as in before I'm to weak and frail to jump in front of a train or similar.
So a handgun to eventually, humanely off myself... would become a priority. I sure wouldn't want to exist as some dieing garbage in a hospital bed.
Then just live out your life as best as you can, with whatever decent time you have left !
It would be a good time to kill anybody you really wanted dead also....I have no such enemy.
If there were a person that had murdered my brother, raped my daughter, etc......, I'd take them down, before I had to kill myself because I'm dieing from AIDS.