It is all about not loosing your head

I played tennis after a week today and against an opponent of comparable skills. I realized that there was a moment in the set where I was leading the set with 4-2 but I ended up loosing it 4-6. After the customary hand shake we started discussing why I lost. The opponent said, "It is all about not loosing your head." He suggested that I was not in well control of my shots towards the end of the set i.e.I committed too many 'unforced errors'. I agreed to him on this and I continued the thought process after showing him my humbleness.

I thought about myself 3 years back when I just finished my undergraduate. Loosing in anything was so hard and it gave so much sourness and distaste despite any shown humbleness for defeat. Why is that I am not that sour or unhappy today after loosing. I guess in 3 years I have learnt loosing with grace. With these well timed defeats, I learn more than I ever can with a success. It just gives such a humanly chill. In-fact, I enjoyed congratulating my opponent.