How do I deal with my body wearing out from years of hard work?

You can weld anything, in any position, and that mastery was bought with years. Now the bill is coming due in your body and your eyes. There is a hard honesty in that, and it deserves to be faced plainly. The work gave you a rare skill, and it also took something. Both are true. It is worth grieving a little, and then getting practical. The years cannot be undone, but what is left can be protected. Your eyes, your joints, your back, they are not infinite, and guarding what remains is not weakness. It is respect for the body that carried you this far. The tough thing now is not enduring more damage; it is choosing to prevent it. So take the protection seriously, even when the old habits say push through. Wear the gear, take the breaks, get the checkups you have put off. And start thinking about how your knowledge can outlast your body, by teaching, by guiding the ones coming up behind you. Your skill does not have to end when the hands slow down. It can pass on.