Jeff Galloway (born July 12, 1945 in Raleigh, North Carolina) is an American Olympian and the author of Galloway's Book on Running. (wikipedia)
The most important force inside you for feeling better all the time is the will to get more fit.
There's an old adage that for every second too fast per mile in the first half of the race, you'll run at least 2 seconds slower at the end.
Most people have this perception that you have to be out there running for an hour and a half every day. But you don't have to give up your career and family to run a marathon.
Here is the start, there is the finish line. Between that, you have to run.
Even world class performers can benefit from walk breaks.
Find a way to enjoy parts of every run. Most of your runs should be mostly enjoyable.
Think chest/hips/ push, or CHP, when it's time for uphill running. Chest up, hips forward, push strongly off each foot.
We have a no puke rule. The purpose is performance, not puking.
If you're laboring up a steep hill, imagine that a towrope is attached to the center of your chest, pulling you steadily toward the top.
To finish will leave you feeling like a champion and positively change your life.