A couple things come to mind. Firstly, it's going to take a while to come to terms with the diagnosis, and you'll obviously find your emotions could go all over the place. It can be a bit like suffering a bereavement and you need to grieve your old way of life, so you might find you go through some of the stages of grief, like denial or anger or depression. They're perfectly normal things to experience so don't be worried or surprised by it. FInding healthy ways to express how you're feeling can help.
The other thing that might help is regularly review your day or week and to notice the things that energised you or that you really enjoyed, that felt like it was really good for you somehow or where you felt alive. And similarly, ask yourself the opposite question - what things drained you or left you feeling empty afterwards. Over time you'll probably notice similar things come up, so then you can start to make better choices about what to do. So as an example, I know that I feel much more peaceful when I've got in touch with nature somehow, whether that's being in a park or watching the clouds. And I know that spending the whole evening watching mindless telly will leave me feeling flat at the end of the night. So I know that, given a free evening, it'll be much better for me if I was to get out to the park for 15 minutes instead of watching some rubbish on telly.
Hope that helps. Being diagnosed can feel pretty devastating it, but it doesn't mean your life is over. It's just taken a new direction.