Yeah, sucks.
I was sick with the flu for about 1 1/2 weeks and got over it 3 weeks ago.
Then when hard into a new training style.
Hadn't trained for about 6 or 8 weeks prior to that too.
But now I'm going hard and probably close to the best I've been with overall fitness.
So instead of thinking of it as the "worst demotivation", why not think of it as the best motivator.
You are over the flu now and ready to make new progress and surpass past efforts.
Sometimes a little setback can be good to put things in perspective.
Progress is never steady when life gets in the way.
As long as you're going up more than down in the long run, thats what counts.