what does this word mean in here?Thank you.
I don’t believe that personal growth should be a side-activity.
what does"side-activity'mean in here?Thank you.

Question

Answer

"Side  activity"  refers to any activity that is not primary activity.   For example,  a student has the primary activity of attending school.   A  "side activity" would be participation  in some sort of singing group.

A person's job  would be their primary  or essential activity.  The hobby of   electronics  would be  a   "side activity".

Any sort of recreation  is a "side activity".   Reading novels would be illustrative of a 
"side activity".

Answer

It means you should not put personal growth should be "put to the side" "ignored" "forgotten".