i have been using a HRM, cateye V3 HR, cadence, speedo, for the last 8 years.
i usually start off in the high 80's low 90's and push slightly hard until i get to 130ish and then ease up on effort a bit, shift into a lower gear or lower my cadence or both, and continue on. i watch the HR go down and adjust effort as i go. if my HR doesn't start to go down when i ease up like earlier in the ride i will stop and take a rest.
it's surprising how a drink of water can lower your HR when riding. as other noted if i push to hard i will get light headed. this is a obvious sign that you are pushing to hard so you should back off a bit.
. everyone's body is different. if i let my HR get to the high 140's my fingers get slightly tingly. if i continue on at that pace my fingers and toes get numb. first at the tips and it moves down to the hands. if i slow down the numbness goes away like it began. also if i go over 150's for long i usually get headaches.
i have a significant family history of heard disease so i have had a lot of tests and checks on my heart. every test results are good so the dock's response is that's your body telling you to slow down and i should listen to it. she also says that what i am doing is good and keep at it. i shouldn't worry about it until my HR goes up for no reason or i get unusual chest discomfort when i get high HR.