Willpower takes energy. You can use it up and wear it out.
Guess what else uses up your energy? Decision making.
Any decision making. What scarf to wear, how much cereal to put in your bowl, what parking spot to choose. All the little decisions you make all day, every day, take energy.
So if you’re trying to make a change, develop a new habit, you need to save up that willpower to use on that, not waste it on mundane decision making.
What can you do? Find ways to automate decision making. There are decisions you can’t avoid, and ones that are fun to make, such as what to have for lunch. But plenty of others can be put on autopilot, such as a standard measure of the same cereal every day. This translates into a more automated shopping list too.
Another strategy is to give yourself fewer options. Choose 3-5 (this seems to be the magic range of options) favorite scarves for the month. You can choose a different set next month (or just get rid of those scarves you never wear).
Every morning, you’re only choosing between a small number and using less mental energy.
It’s been shown in studies that just thinking about options without having to choose between them is much less stressful. Try daydreaming about what you might have for lunch before you arrive at the decision point to prime yourself for an easy decision.
Pay attention as you go through your day and notice what decisions you make that you can avoid or restrict your options for.