Actually, being serious for a moment.
Make a pledge, there's still 6 months of the year to go. It'll give you motiviation for something daft in the latter half of the year.
I've pledged to do one each of 100k and 100mile rides per month (which isn't much of a stretch tbh) and to ride one 200 mile ride. (Which blimming well is).
When I rode with Kajsa back in February, there was plenty of time for a good chat. I remember speculating that with all these guys heading off for a ride with this mysterious Swedish lady they'd met on the internet, there must be quite a few wives/partners wondering what's going on. Cue much laughter - unsurprisingly this had come up quite a few times before. Rather more tellingly, Kajsa then commented that since starting the challenge, one thing that had disappointed her was finding how unusual it seems to be for couples to enjoy cycling together.
It would be very easy to make a sweat pledge involving physical challenges, but I'd be planning to do them anyway. In view of the conversation I've outlined above, much more apposite would be a challenge requiring me to see my wife enjoying cycling again, as she has in the past. So that will be the basis of my sweat pledge, whether or not I ever register it on Kajsa's site.
xx
(for Kajsa, hoping she reads this one day)