[sarnu]

> I guess it's related to personality types.

This and it also depends on your experience. When I started running I also used a heart rate monitor and training plans guided by an app. By the time I got a feeling how fast I can run I ditched the heart rate strap. Now I still use a running watch with gps, but do not let it set my pace. On the other hand, I'm not ino competitive running, I'm doing it just for fun.