When I was 50 I had a lot more energy. I had also had cancer, and had had many friends die of that same cancer (people I met through an internet support group initially). I've now had even more crap happen to me that has wrecked my health in certain ways.
I gave notice 2 weeks after a close friend dropped dead at 67 but I was planning to retire around then anyhow. However, that death shocked me to the core.
You don't know what your health will be like but I'm sure it will be improved by being able to take it easy and garden and so on! But most importantly, retire while you still have the energy to take advantage of all that spare time and don't put off stuff you want to do. You will be amazed at how busy you can be if you want to, and how full your life can be in retirement.
The only activity-oriented advice I can give you is to try living on less money and make sure you won't miss the treats a lot of spending can provide. But don't wait too long
Also read a lot of posts on this forum. They are really supportive of this kind of move.
I'm thrilled to be retired and doing a lot of traveling now while I have some energy for it. I never thought my health would be so compromised but it was. Go have fun.