first-time tennis in a long while

I played tennis with my boyfriend this morning. We had 2 hours, but it was enough to enjoy tennis for 2 person. At first, we continued to play 30 minutes, then take a break around 5 minutes. After that, we started to play again. However we were so tired that we couldn't continue to play for 30 minutes. I felt I got old. From today, I will build up my physical strength.