I haven't used a heart rate monitor in years. HRM data is interesting but not really useful for me. I never bother to try to stay in a particular zone.
I go more by perceived exertion, and sometimes I set a goal for average speed for a ride. Usually I do that when I'm by myself and riding a route that I am very familiar with, so I know what my average would typically be for it.
Something I read a few years ago that I thought made a lot of sense -- if you're keeping a training log, note your mood along with the usual information like average speed, cadence, distance etc. If you're finding that you're consistently not happy, it's a sign that you're overtraining. (It could also be a sign that you just really do not enjoy doing very long bike rides, which was the case for me. I'd much rather do a 65-mile ride and be happy than a 100-mile ride that leaves me feeling like I have to force myself to keep pedaling.)
Another thing about mood and overtraining -- make sure your training plan includes easy days and or days off. Otherwise you will burn out.
- Gray 2010 carbon WSD road bike, Rivet Independence saddle
- Red hardtail 26" aluminum mountain bike, Bontrager Evoke WSD saddle
- Royal blue 2018 aluminum gravel bike, Rivet Pearl saddle
Gone but not forgotten:
- Silver 2003 aluminum road bike
- Two awesome worn out Juliana saddles