In a New York Times article, "How to Build Resilience in Midlife," Dr. Dennis Charney, a resilience researcher, advises that you can increase your own resilience by going outside of your comfort zone. "There is a biology to this. Your stress hormone systems will become less responsive to stress so you can handle stress better."
Being positive or optimistic is another key, and this is something that can be developed. In his book Everything's an Offer, Robert Poynton talks about how improvisers on a bare stage must use all ideas--even accidents--to create the seen. When you can frame setbacks as offers to be explored, more possibilities open up.
So say hello to a stranger, wear something fun, extend an invitation, and get out of your comfort zone!