Tugging

Juz finished sch Student Council Investiture. At the investiture, our ex-principal went to support her niece, who is also our student...
Upon seeing her, I suddenly felt like missing her. I didn't work with her for long, only abt 1 year, on & off.. When she recieved the sounding round of applause to welcome her back to school, I felt tears welling up, which I immediately controlled.
Why do I feel this way ?