Learning from chance. Many times we change our routine without concious thought. You do A before B or use the other hand and so on. If you pay attention it will pay back (horrible pun but hay I like it) Your body and sometimes your brain (the nerves extend to the entire body and it evolves as much as you use it wisely) tell you that there is a better way or that one drill should be different. I for one prefer the set movement before the improve ones. It works better for me. Check what works for you. Know yourself.