Here is the posture test - whatever position you are in, maybe right now you are sitting, can you move in all directions – forward, backward, up, down, left, right?
If yes, then you have the advantage of being positioned in the middle of multiple options, a place which allows you to shift and adjust according to do what you want to do. If there is a direction that you can’t move in, then you are stuck; shifting and adapting is harder and requires more effort. It becomes even harder if your muscles have been maintaining that position for a while and are getting habituated to holding you there.
Try it out in your chair right now – can you move easily in every direction?
If there is a direction that is more challenging, alternate been that direction and its opposite, shifting back and forth between the two until you get a sense of where a middle place might be and see what it is like to be positioned here.
If it is unfamiliar, try this new place on for size and do the direction test again from here and see what this posture / place / position allows.
So rather than trying to maintain a notion of straight, look for where the weight of your body is in relation to what you are doing and test whether you are able to move forward, back, up, down, left, right, equally easily. This is the neutral state for optimal action/movement potential that massage is assisting your muscles to return to.