First off howdy to ya and welcome.
Supplements I'm not taking a multivitamin like Centrum because a lot of those vitamins don't work well together and just end up canceling each other out. I'm not exactly sure how to explain that, but my doc and pharmacist both said pretty much the same thing. I take Vitc C for boosting my immune system, Vit E because of all the skin/nail problems, Glucosamine Chondroitin (not the one with sulfates) for my dear bones because as my doctor put "dear you have the bones of a 50 year old" - I was 29 at the time; my chiropractor was less thrilling when he showed me the neck and back of an 83 year old and it looked like my x-rays! ACK! Vit D cause its the sun vitamin and I forget now why that's important other than I work overnights. Fish Oil and Flax Seed Oil b/c I have the early stages of cholesterol showing up in my arteries. I've found that they have other benefits as well especially the Flax Seed Oil and my digestive system. Since i started it I have not had any boughts of constipation/ diarrhea which is always a bonus! I'm sure as time goes on I may add or remove some of these since I have not always taken these supplements.

Overdoing or as the case may be not overdoing it and pulling a muscle, injuries. I hate to say it but I've pulled muscles in my sleep. Gardening, and my other "normal" activities take some planning on my part. I do some gentle stretching and start out slow before tackling anything too taxing. Afterwards I almost always head for the shower or the hot tub. I will even go so far as to take my pain medications and muscle relaxers before I do "normal" things just to ease the aftermath of "pushing" myself. Biofreeze is one of my favorite products. You can get it on the web, from a good masseuse or chiropractor. It's like Icy Hot without the stink. The ice packs are always in the freezer or cooler and the heat packs are near the microwave before I start any activity because I never know until the pain hits which one I'm gonna need. I keep a nice lavender or mint scented lotion on hand for post shower, because the scents are so relaxing. The thing is the everyone even "the normals" do these same things when they push their bodies too far. Just because our bodies are more easily pushed doesn't mean we're all that different from them; instead it means we plan better for the pain we know will follow.