So it depends on the spell, but I think you are talking about summon nature’s ally. That allows you to give instructions to creatures who can understand, and they will fight to the best of their ability, but as a DM I wouldn’t interpret the spell as written to include suicide.
But even then, a good DM doesn’t put a tarrasque into play and have it sit there and die. Once it realizes it is getting damaged and can’t retaliate, it can burrow from we whence it came, etc.
So I think most of the strategies involve weak roleplay from the DM, munchkin builds, liberties with the rules, or both.
Even then, actually killing the tarrasque requires a wish spell, which is not something that a 9th level druid can do.
Physical therapy if you have any physical issues at all, massage therapy if you have any chronic pain, occupational therapy if you have specific life skills or mobility needs.
Any preventative screening or vaccines. There are various generic cancer screenings, etc. Get a referral to a dermatologist to do a once over your skin and document any spots of concern.