Sugar, I just wrote a post about weightlifting, but I didn't say the part I've been meaning to say to your post on falling apart. I guess I think two things.
Thing the first:
I fervently believe that your body loves you and wants to carry you strongly and comfortably. I believe that it is never too late, that it will always respond to you. It will forgive any amount of neglect or abuse, and it will always, always respond favorably and predictably to doing the things it needs. It needs good fuel. It needs to be used, along the whole range of intensities. It needs sleep. It needs daylight. It needs touch and (for many people) sex.
Your poor body. It is mute and it is trapped there with you. It can't say what it means. It can only send you signals, sensations that your bossy, dominant mind can ignore. Your mind wants other things, like information to chew on or distractions. It will find them while your body tries to get attention. It sends lethargy or a pounding heart to tell you you didn't eat what it needs. It sends an ache to ask you to please twist and bend and lengthen it in more directions. It sends joint pain to say that you've gotten out of alignment, please come back to your spine and work from there. It gets weak when it wants you to know that you should fight your limits. As soon as you do, it will rejoice by pushing those limits away and teaming with you to charge down the new limits.
As soon as you are moving in the right direction, you have no greater cheerleader than your body. It LOVES you. It is SO EXCITED to do things with you. Your body wants to go on walks with you. Your mind is seeing things and whirring through the details of the day. But your body will send you rhythm between your legs and your breath. Your body will give you pink cheeks, or that delicious sweatbreak. Your body will thank you for sufficient nutritious food within a day, with a steady grateful energy that makes the Diet Cokes unnecessary. Your body CANNOT WAIT to pick that up, and here your mind should urge it to go a little slower, focus on technique. Because your body is JAZZED! It loves hefting things! It floods you with euphoria after! It begs you to throw that heavy thing around afterwards! Then jump over it! Maybe roll on it! It all feels good! Do more! Your body is sort of a golden retriever puppy. It has no sense. But it loves you and it wants to bound.
Thing the second:
Neglecting your body is sad, because it is a mute creature that is at your command. We should tend our bodies as we would tend any creature under our control. It is sad because it the feedback is so immediate; the signals come as soon as we move in a direction, healthy or neglectful. It is a shame to pass up that source of gratification. That said, I know it is hard to fit it in and the world is full of distractions from the pleas of your body. I fully think that working out as much as I do is a selfish treat. I'm lucky to be able to do that because I don't have other strong demands on my time. I don't know how I'll balance it when I have a family with equally good claims.
If you can make time, I think you should. If you are basically healthy, you can repair your body and bring it to whatever state you want it to be in. After a lifetime of rolling my ankles in sports, they are now fixed, by strengthening and a lot of painful massage that realigned my legs. You can make your body stronger than you dream, or fast or bendy or springy. The ways to do this are known; your body will react in predictable ways. You just have to make that What You Do for a while. It takes a pretty wholehearted focus (which is fun, when it is fun). It is never too late. I see people at my gym make drastic turnarounds, to become glowing and pink and proud of themselves for doing things they dreamed they could. Your body is on your side. If you do this, it will give you every help and encouragement it can. It will send you good sleep; it will crave dark green foods; it will breathe deep and full; it will grow strong; it will be euphoric; it will wake and feel alive. It loves you, and you will feel it.