It is easy to fool yourself by saying, “I will go to the gym. I’m just gonna watch one more episode of my favorite tv-show”. Most people will, in that situation, most often not go to the gym. However, if you instead have the self-discipline to tell yourself, “I will watch one more episode, but only when I come home from the gym”, then you can be pretty sure that you will do both.
The sequence in how you do things matters, and you should acknowledge that and use it as an advantage for yourself.