Ask HN: Smallest/simplest change possible with maximum benefits

Hi, when we read books or follow advice to improve our life (or finances/social skills/fitness etc), many a times these advices suggest a change which is not necessarily easy to implement, requires lot of perseverance etc.

I am looking for very small or very simple or very clever changes you made in your life or thought process which had the biggest impact possible in your life. Not sure whether my question made sense or not, but do reply if it did.