Reasonable expectations and goals. Sure You can push yourself to complete a goal successfully but if it is too ambitious Well I personally burn our much more quickly.
I agree with @Adirondackwannabe listen to your body… well after the warm up anyhow. It can be hard to ignore others and people who “are better” do it anyway keep a log.. You will improve faster then you think actually are when envying or when forcing your body to comply with your schedule and goals. The only thing I would really be good about observing is the regularity in which I worked out. And remember we all have bad days. So just showing up and trying can be achievement.