A comment I get a lot in regards to my welding....I "must have both." The truth is, I've got neither. I'm legally blind in my left eye, I'm near sighted, and I've got horrible double vision. The more I wear glasses, the quicker the sight goes downhill...so I don't often put them on. I've thought about laser surgery, but considering the amount of time I spend looking at a weld pool I'm a little nervous about light sensitivity. So no, I don't have great eyes.
And I remember back to my first welding class at Macomb Community College, when I was an apprentice at Chrysler. Before we got into tig welding, we did a little bit of oxy/acy welding. The instructor did a demo for us: torch in the right hand , filler in the left hand, both extended far from his body. And he put down an even, consistent, 6-7" bead. Steady as a rock. I recall turning to a fellow apprentice and saying "If you've got to be that steady to weld, I'm out." I shake like a leaf. Always have. I'm sure my penchant for Monster and Haribo gummies doesn't help the situation, but that's neither here nor there.
So from the start I've used every trick I could pick up to mask my shortcomings. With the eye issues, there's only so much you can do. I've learned that "vision" and eye sight are two different things. With 20/20 sight there's no interpretation, no grey area, what you see is what you get and you can attack it. But with vision there's the added elements of anticipation, of making *educated guesses*....of feel. So I depend on my vision much more than my eye sight. To be honest it's not always the perfect compensation, but if given the choice I'd much rather have pure vision than perfect eye sight.
On to the steady hand. There was a journeyman I once worked with that told me a bit about how he was trained. When he was taught to weld, his instructor told him to be as "uncomfortable as possible" when practicing, because then you could weld in any situation. What a flawed concept! And proven out by his pupil, who was not a good weldor. Yes, you're gonna be put in some awkward positions and you'll be expected to perform. But no matter whether I was in a swaying boom lift repairing an overhead door with a stick welder, flat under a car pushing the tig pedal with my knee, laying on my back pulse welding under a 70 ton tank, or upside down in a stainless washer welding with a mirror while my partner held a shield in front of my face because my helmet wouldn't fit through the opening, I got as comfortable as possible in that situation. Once you become orientated, welding is welding, and your training/experience will take over.
Think about stick welding. You've got a stinger, then an electrode beyond that. Any uneasiness in your legs goes into your body, then goes through your arms/hands, then the stinger, then the electrode...and it's amplified the farther it gets away from the source. Even a little twitch in your hand is gonna be a big twitch at the business end of the stick. The closer you can rest your hands, arms, and/or body to the work piece, the better off you'll be. Obviously this is harder to do in some circumstances than others, but don't be afraid to think outside of the box. I've even seen guys take brooms and place them against the pipe they're welding on in order to have something to lean against. I'll take vice grips and attach them close to the work area to rest a hand or arm on. When welding under the tank, I grabbed a tall 90* angle block to lean one of my outstretched arms on, which helped steady both. Outside of that, a proper stance helps as well. Like a MLB hitter in the batter's box or a boxer in the ring, find a stance that will keep your body as steady as can be. As you work your way up, keep your elbows tucked in as much as possible and your arms in line with your body. These general ideas work for any type of welding, although with tig you've got the additional problem of keeping the filler rod steady, and in many cases operating the foot pedal as well.
If I'm sitting at a bench tig welding, I don't need to worry about my lower body. The main things to keep steady are my arms and hands. I'll keep the work as close to me as possible, and I'll keep my elbows tucked in to my side. When you're using a long piece of filler rod, a wobble at the back end can make it more difficult to control the other end at the puddle. I don't often do it any more, but a trick I was taught back in the day was to bend a 2-3" section of the rod to a 90*, at the opposite end of where you're melting it. The bent end would always be weighted in the "down" position, and it would keep the rod steady instead of it wanting to flip around. Another option is to actually tuck the rod between your arm and your body, holding it steady. But I'll usually just hold the rod with my fingers, "pinching" it, giving it tension so that it presses against my arm, rather than letting it float in space.
When possible, I'll rest the wrist of my torch hand as close as I can to where I'm welding. Sometimes I'll just hold the torch with my thumb and forefinger, using my pinky and ring finger to steady myself against the work surface. In any type of welding, the closer you can get your hands to the arc, the steadier you can be. The closer you can rest your hands or arms against a solid surface, the steadier you can be. It's not always possible to be that close, but it's the general idea...closer = steadier.
However, there is a downside to resting your torch hand that close to the weld. It increases the difficulty in making a long pass. When I tig, my fingers, hand, wrist and arm must move in sync to keep the torch angle and arc length consistent as I creep my torch hand along the weld. There are many more moving parts, and a greater chance to screw up than if you're able to hold your torch hand above the work piece and use your arms and body to "rotate" down the weld, or slide almost as if on rails. If you're steady enough to do the latter, it's the way to go. I'm not, so I improvise with the former technique when I can.
So even if you can't see all that well, and you don't have that steady of a hand, you shouldn't let that get in your way. Maybe you have to resort to an unconventional method or two, but if that's what it takes, so be it.