Is it normal to develop healthy habits when you're sad?

When I'm content or happy, I do nothing and just proceed with life, eat more junk food than healthy and hit the gym less. When I just bawled my eyes out the day before, I tend to be more motivated and confident that I will wake up at 5 am to meditate then exercise. I also would rather eat a bowl of salad. I think they may be a coping mechanism or my way of I guess fighting off negative energy or thoughts.

+I noticed this after my friends made me sad yesterday because they joked about something I'm extremely insecure about. I usually laugh at myself and their jokes about me because I'm not insecure about it or I know it's flat out not true. But the thing they joked about was true and I'm positive they didn't know I was insecure about it. But it just made me want to improve that skill, which I know is a good thing, but the weird thing is my drive to want to be healthier (exercise more, eat healthy, etc) because it literally has nothing to do with the situation.

Also, I could totally see how the joke they made is harmless in their eyes (they joked about a communication skill I lacked) but I low-key feel like it's affecting my social relationships with newer people and I kinda need that skill to be successful.