That's why I don't run/walk - I would just end up walking. I totally believe in it and think I would probably be faster if I did it, but I have zilch discipline for switching off like that - it's a lot of work and requires more mental toughness than just plodding along IMO. I deeply respect the people I see at races doing it. I have always been very consistent with my pacing even in the latter stages of races but I wonder sometimes if it's good. All the stories of champions I've read have portrayed their early days more like you - too fast and then the great burnout. You just learn better from mistakes.

I injured myself on this steep, deeply cambered downhill in my last half - I was in horrible pain and it never occurred to me to just stop or walk, just stupidly stubborn. I had 5K to go and every muscle and tissue in my pelvis started spasming and screaming "no". I had no idea I could hurt myself in the area 9if it was my hamstring or Achilles I would have stopped immediately) and I ended up with an ab muscle torn off it's connective tissue.