OK, I do have an HbA1c in the 5s, but I wouldn't say I have to strive very hard for it. I'm sure that it is partly luck or perhaps I still have a bit of my own residual insulin which helps.
I've certainly realised on these forums that some people seem to have far greater difficulties in control and their glucose levels fluctuate far more than mine. What I do works well for me, at the moment. It might not for ever. It would't work for someone else who had more volatile glucose levels than I have at the moment..
My doctors used to be worried that my levels were too low, and at one time they were right, as I was losing hypo awareness. Now I use a pump and I have fewer hypos and I catch them before they are too low. They have seen what my glucose levels are doing on a continuous glucose monitoring system and they are happy at the moment.
I exercise a fair amount, mostly running, daily swimming in summer and Pilates. I don't do it because of diabetes, I did it before I had diabetes and when diagnosed was determined to carry on. In fact it motivated me to run my first marathon. I know that this keeps my fasting levels low, if I miss it for a few days my fasting level rises.
I still have some hypos, not very low, normally in the 3s. I've done a lot of testing and they are mostly totally predictable ... though even on a pump not totally avoidable, (I'm getting better at it. ).My hypos, occur during or several hours after exercise and at the moment I seem to be fortunate in that I seem to be able to treat them very conservatively. I use a couple of dextrose tablets, recover very quickly and carry on with what I am doing.
I carb count always, and when at home normally weigh starches. I eat a moderate amount of carbs, similar amounts daily because I'm a creature of habitnot because I think I have to but it might help. If I eat out I probably eat more flexibly and sometimes get it wrong. I don't snack but never have, I live in France where snacking isn't normal so there aren't the temptations there are in the UK. It works for me, in fact I'm shocked when I get the odd high post prandial level.
BUT what works for me might not get anywhere the same results for someone with a different metabolism.
edited to add; One thing the DCCT found was that people with similar average blood glucose levels didn't always have the same HbA1c! One might have a HbA1c much lower than another, another reason for not making comparisons.