Every aspect of life is bound to shape itself over the long run. Health, success, relationships, even belief systems… these are all build over time, never in an instance. Hence deciding upfront about how they are going to look like, and what values you are about to associate with any of them is a rather big deal.
If you decide that healthy food is an important factor in your life, and that you will never under any circumstance allow yourself to eat junk it is all set for your health to be dramatically improved and maintained over a longer time frame.
If you decide that you will get up early in the morning so you can aspire for more and do more in life, then, no matter how tired you feel once the alarm goes off you know what you must do.
If you decide that you will act a certain way in a particular occasion or set of circumstances, then there is no emotional response that would make you behave otherwise. It is already being decided.
If you decide that you will behave a certain way toward your friends or family or significant other, then no matter what happens you will stay true to your values. Like when people try to justify cheating based upon some emotional response or certain stimulus- If you have decided that you are loyal to someone, or something, then there is no force that will make you act out of sync with what you have decided. It is really that simple.
If you decide that workout is a must any day of the week, then there is no excuse that will make you skip one.
The thing is that once you decide about how some areas of your life are going to be, slowly but decisively you will get there. Not letting passion and emotion in a certain moment to affect your decisions, regardless of their gravity, will bring your life in sync with what you’ve decided for it to look like. But for that you need a system of planning and setting your priorities upfront.