FWIW, I was in the position in my mid-30s where my partner was diagnosed with uncommon type of cancer. That particular subtype had an extremely low 2/5-year survival rates associated if it went metastatic.

Most people are going to suggest avoidance strategies. That does work to an extent. You can try to firewall your personal life from work. It doesn't stop intrusive thoughts, other people bringing it up in conversation, or finding something that will remind you of it.

What helped me the most was the opposite - I took to "negative visualization" from stoicism [1].

Meditate for 15 minutes - visualizing one possible negative outcome, really live in those moments, imagine what your life would be like, what hardships you would face, what you would look forward to in that situation. After that 15 minutes, take a deep breath - and realize that hasn't happened. Savor the little joys in your life.

For my particular situation, it helped with mindfulness. I would actively seek out and create those moments of joy.

[1]: https://www.amazon.com/Guide-Good-Life-Ancient-Stoic-ebook/d...