de·cide verb \di-ˈsīd, dē-\
Definition of DECIDE
a : to make a final choice or judgment about <decide what to do>
b : to select as a course of action —used with an infinitive <decided to go>
c : to infer on the basis of evidence : conclude
: to bring to a definitive end
: to induce to come to a choice
The most important part of this word is the ending. Decide means to kill off your options. That means, to make a choice, so that there is no going back.
That's why making a statement of purpose is so powerful, because when you declare it to the world, you are asking for the world to support you, you are making a stand. Saying, "I will do/believe this."
Ah, but the fun stuff happens when the universe talks back. Don't click me off here, I haven't begun to hear voices, well, more voices, I mean. Haven't you decided to go on a diet and the very first day get offered your favorite red label food? Haven't you told someone you were a writer, to have them ask you how many books you've written and where you are published?
This universe is testing you. Making sure you really decided, not just giving lip service to something.
Having goals is a way of deciding. They have to be measurable and a stretch to what you would normally achieve. They should have a stop and start time, and they are best when you show them to someone, not keep them in your drawer or under the cat food.
Decide today one little change you're going to make to get something accomplished you will feel good about tonight. Do it for yourself, but tell someone else you're doing it to make it more real, so you risk more.
And kill off your other options.