In sitting meditation, is it okay to lean forward when it feels like you're falling back, even though you are averting some pain?
But I do it mindful, noting everything, or should I just force the position?
Avoiding pain is different from trying to keep your sitting position.
So if you start to fall backwards so that you actually can't keep your position,
And I don't see what's wrong with pulling yourself back mindfully.
You can consider it to just be an appropriate act.
It doesn't have to be because, oh, I don't like what's going on.
It can be, but again, it's one of those benign, even if there is a desire involved, the problem with the desire or the aversion to the pain
aversion to the leaning back is going to be far less disruptive than having to fall back and readjust your meditation practice.
Far better off to bring yourself back and say, no, no, my intention is to sit straight.
Now if you mean like having to sit up perfectly straight, then in vipassana it's not considered to be advisable
because you're not developing in vipassana without samatha because you're not developing high states of concentration so you're going to have the pain whether you slouch or whether you sit up straight unless you're developing samatha meditation so that you're not going to benefit from trying to sit perfectly straight but when you're falling over well write yourself say moving moving come back