Actually it is not easy to stand straight. You may often stand while leaning against the wall, planting your hand on the desk or on your hip. When you think too much of standing, it may be difficult to relax your body. Your heavy head, trunk and bilateral arms may not be in the normal positions.
The way you stand would be in some degree affected by your habit and daily life style. Even your occupation and belief might be associated with it.
In my case my head is often tilted to the right without knowing. Not until I started yoga lessons, did I realize that I have a pain in my right neck. To avoid causing pain I seem to tilt my head to the right unconsciously.
For my healthy body and mental attitude, I will encourage myself to stand strait!
Blue Rock Thrush came again in my balcony