To "take a step back" means to think about a topic in a more complete, less emotional way:

I was extremely upset when I got laid off, but after a few weeks I was able to take a step back and realize that I still had what was important - my health and my family.

If you take a step back and think about it, college doesn't really last that long. It's just four years out of your life.

Do you ever take a step back and wonder why so many people wear glasses in modern times? Our ancestors wouldn't have had glasses, so how were people able to see back then?