If I don't cycle, then I have no transport. Last week I cycled Tuesday through to Friday, plus Sunday. Thursday was by far the worst day here - on one (slight) downhill section which was directly into the headwind, I could not hold 9mph downhill and having to cycle downhill is just not fair in my book.
Coming home along that section going uphill with the tailwind I was easily holding 20mph despite having not had lunch (and I'm not good when I miss food). For once, and it has been the only time, going home was much quicker than getting there. Other than finding it more tiring, I have found that (assuming you make yourself visible to motorists) motorists are generally more accommodating in bad weather than they are normally, but they have to be able to see you.
I have (or at least tried to) cycled in conditions where at times I could not stay on the bike, where I could not actually keep a fully laden bike on the road (but not quite like that video - great but as my husband would say, those bikes clearly don't weigh enough!) - we had no choice but to carry on that day on tour (exposure was a serious concern, the only time I have considered sleeping the night in a public toilet). I look back at our 12 month tour and I know without a doubt that they were the 2 hardest days - when you can't actually keep the bike on a 2 lane road, you know it is time to quit cycling and take a few days off.