Animators act out scenes in front of a mirror to see how a real body moves. Use your own life as reference.

You are carrying the reference material around with you. Rather than guessing how a body reaches for something or slumps after bad news, you can do it and watch, which gives you detail no amount of imagining produces. Professionals do this routinely and it looks ridiculous, and they do it anyway because it works.

Act out the thing you are trying to draw or write before you draw or write it. Do it in front of a mirror or film it on your phone. Watch for the small stuff you would never have invented, like what your free hand does while the other one is busy.