This is something I try to remind myself often whenever I find myself thinking too much about my life. Oftentimes, when I'm thinking too much, I just end up getting depressed.
The basic premise is this: In the everyday grind of life, that's when you should be observing, taking notes, gathering intelligence. Then, each day, take a step back and assess:
Then go back to the grind and act accordingly.
Both learning on the ground and reflecting in the tower are essential: they complement each other.
If you learn too much on the ground without reflecting, then while you may be enjoying life and keeping yourself busy, you most likely won't end up enjoying where you end up.
And if you reflect too much in the tower without learning on the ground, then you'll find yourself getting depressed with how much you're just standing still, not doing anything.
Learning on the ground is about the present; reflecting in the tower is about the future.
Keep a healthy balance between the two, and you'll find yourself accomplishing great things.