You ask a really excellent question!  I do believe that a good part of maintaining mental health is being resilient.  The word means a lot of different things to different people but to me it means being able to surive adversity.  It means when bad things happen...like you say...you are able to bounce back.  Why are some people more prone to being resilient?  That is the million dollar question. 

I am glad that you have this quality.  It has helped you and will continue to help you especially if you battle depression.

I found a really good article about what being resilient means as well as how to promote it.  This article is about children but I think it is general enough to include adults as well.

Thank you so much for your question and I would love to read what else you share here.