It's annoying, having consciously to control what used to be automatic.

Awareness that one is wobbling and wibbling is the first step, so to speak.
In the end, only you can control your gait. No therapist can do that for you.

What gets me is the premature fatigue that sets in if I walk too far, or what my legs seems to regard as too far. The lower legs eventually go on a sit-down strike. Some degree of regular exercise, I mean muscle-building exercise, may help but it seems to me that the nerves just stop transmitting

In terms of gait, I find I walk better if I straighten my legs each stride, a strut almost, and plant my feet firmly. So I put the foot down and then as the leg moves to the vertical, I straighten it, push back against the knee joint.
The opposite, the bent knees, worked for Groucho Marx of course.