Undergraduate / "an elderly Alzheimer's patient"- one of your extracurricular activities (common app) [3]

I need a little help with this essay, I'm not really sure it's relevant or sufficient for the common app. It has a 150 word maximum. Thanks!

One day last summer, I was sitting outside with an elderly Alzheimer's patient named Mary at the nursing home where I volunteered. We talked of silly things like cats and flowers for over an hour in the warm sun. When she felt it was time to go inside, Mary said to me, "I really want to thank you for coming out here to spend time with me. Since I'm not allowed to go out alone and many of the nurses don't have time to go outside, it's a very rare and joyful experience just to go outside for five minutes. You are a lovely young lady, and I hope you realize that even the small things do matter." This was the moment that I realized that my true talent was in serving others because it made me feel good about myself, and I believe that in giving, you also receive.