I read a book called 80/20 running, that pointed out that most of us run most of our runs too fast. It made a huge difference in my training, to run at (say) 60% of my pace most of the time instead of 90% as most of us do. I felt better, I enjoyed it more, it created less anxiety to start a run, I recovered faster, and I could log more miles per week.
I feel when you push yourself too hard it will make you look less forward to your next workout. Best to end on a good/interesting note similar to how TV episodes do - making you want to come back for more.
