While my sister Mallory and I may look a lot alike, there are some striking differences between us. One of these differences is exercise. Simply put, Mallory likes to exercise, and I don’t. For as long as I can remember, Mallory has made exercise a priority in her life. She has repeatedly told me that exercise helps her not only physically but improves her mental and emotional wellbeing too. I just rolled my eyes.  About two years ago (I am embarrassed to admit), vanity got the best of me. I was asked to be in a wedding party where, on average, everyone was 8+ years younger than I. While honored,…