take a step back and (do something)

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?

college

When Americans talk about "college", they probably mean a 4-year college or university.

In most other English-speaking countries, people differentiate between “university” - a four-year university with research and graduate programs (you may hear “uni” used as an abbreviation) - and "college" - a “junior" or “community" college.

Here's a full explanation of the difference between "college" and "university".

a period (in someone's life)

When something happens to a person for a few months or years, you can talk about that as "a period" in that person's life:

His teenage years were a very difficult period for him.

You can use the phrasal verb "go through" to talk about a period in someone's life:

It's not uncommon for retirees to go through a period of depression soon after they stop working.

Note that you can also talk about a historical period.

a brief (time)

The word "brief" means "short". You can use it to talk about a short length of time:

For a brief period in the late '90s I was really into modern dance.

There was a brief moment where I thought that they were going to start punching each other, but then Chuck apologized and they shook hands.