Tip - Go as far as you can and then 5 minutes more.
This tip is for exercise. I was reminded of it during my 'accidental' 5K last week. It started as a simple 20 minute run and ended up as 3.1 miles+.
I ran as far as I could, walked for a minute to regroup and kept going. I found out this is actually a strategy of marathoners. I thought they ran the entire way, but unless they are of a professional grade, they likely slow down and even at times walk to rev their engines back up.
When I read that fact, I felt freed. I thought I could not be a good runner because at times I was forced to walk. Now I know that I am making my best effort - period.
So no matter what your cardio of choice, do it the best you can and then try to go a little further. But never fear having to take it down a notch, it's all part of the learning process.
Yours in fitness, Kate