It may be hard but letting go is your option to heal from this. I had many pet beta fish that I always treasured and seeing them suffering until death always hurt me deeply, the fact that I couldn't do anything to save them made me feel helpless, but I eventually let go of my grief after they died.
Squidboards
Cephalobro
solz
[spolier]this happened to me Last year took me Like 3 months to get over it but my friends helped me through it good luck 