We make plenty of choices every single day. When you look at these choices closely you can discern that every little choice has the potential to build our character in one way or another.
When you make a choice whether to exercise or watch some TV you in fact choose between strengthening your willpower and making it weaker.
Every time you choose between wearing something comfortable and something that you'll look good in, you choose between more self esteem or the less of it.
Every time you choose between a healthy, whole plant based food and some processed, addictive, toxic to your body product (most likely some innocent animal been tortured and killed so you can "enjoy the taste"), you choose between health and disease, strength and weakness both of your character and your body.
All these "little choices" build our character every day and most of the time we are not even aware of that. They make us form bad habits and soon enough, instead of even thinking about exercising you reach for the remote, grab a bag of crisps and let some negative information on the news sink into your brain.
On the other hand, every small win, every good habit, no matter how small, makes you stronger. It all adds up, little by little, giving you more and more power to tackle the challenges of life.
When you take care of the small things in life, the big things will take care of themselves (and if they won't you'll have the will, strength and cohones to make them happen)... :)