Occupying my mind

I am stage 4 with colon cancer, 36f, terminal or whatever they say. Onc gave me 2 yrs and estimated that I've had this for 5-10 years already based on progression. Treatment is going well in that it hasn't taken too much out of me, I still have energy and a mostly functional mind, less some brain fog.

My problem is - how much should I let my diagnosis take up space in my mind? I feel borderline obsessed at this point, it's hard to think about anything else. Some of it is productive, like planning trips with my family and getting things in order for when I'm gone, but still -- it feels like the only thing I think about and I'm not sure the line between processing and obsessing.

How do you all keep your thoughts moving and processing without going too far into the bleakness of it all?