Even if you don't stop for yourself think of your loved ones.
I'm not that much in to it, thought it was something I could cope with, but now both my kids are also walkers. My daughter is doing her second 50km challenge in a couple of weeks, after the first one she swore she would never do it again, promised that was the last time, but she just couldn't stop herself.
So my advice is to just say no and walk away...
...just lace up your boots and walk away.....
...rucksack on, boots on and just walk...
It's fine, I can handle it, I'll just sit here quietly rocking and sniffing a pot of dubbing