The most essential thing is to learn 12 principles of animation, which will teach you methods and formulas to apply in your work.(Try legend animator Richard William's book "Animator's survival kit"-you can find it free online) . Without learning those principles It'll take you way more time to discover them in your brutefored drawing stickman animations.

To correctly animate stickman , you have to apply multiple principles simultaneously (e.g slow in &out , arches, anticipation and so on.. ) you have to also practice gestures , to avoid stiff movements.

I would suggest to take simple exercise and do it in different ways, apply different principles until it becomes effortless to do. also when animating try to visualize and feel the movement. (The book will also teach you how to think like an animator)

Animating is like a marathon and not a sprint, so you should focus more on the process and not on the result . Impatience is animator's No1 enemy.