If you make your bed every morning, you will have accomplished the first task of the day. It will give you a small sense of pride, and it will encourage you to do another task, and another, and another. And by the end of the day that one task completed will have turned into many tasks completed.
If you set aside two minutes at the beginning of your day to make your bed, even if you accomplish nothing else all day, you've done this one thing.
Making your bed is a healthy habit that ensures you start your day with something accomplished, and by doing so you elevate your mood. Even if that one task is a small thing, it can make a world of a difference to your mindset for the rest of the day.
Also, the sight of a made-up bed can send a signal to the brain to make sleep more appealing and less vulnerable to disruption.