It is not just okay, it is the most sensible and productive thing to do, as long as you find it meaningful, and feel no guilt about it.
It would even be better if you spent that time being kind to people, helping others, enjoying good music, watching good movies with song and dance, have your favorite ice-cream, explore how best you can establish peace and harmony among the people of the world, and share some clean jokes with friends.
Spurts of Thought 