Had to use a mental health day and it probably saved my life

Was having a really dark day last Thursday. Not suicidal but just... done. Called in to work, told my wife I needed the day, and honestly just sat in my car at a park for a couple hours.

Did nothing. Read a book. Breathed. Didn't go home, didn't try to "be productive" with the day.

Came back Friday feeling human again. Told my boss I was dealing with some stuff and need to keep Monday mornings lighter going forward. They were fine with it. Why did I wait so long to do this?