Happens to the best of us.
I played for a long time thinking that it was 3 failed saves before an extended rest and you died.
Thats the way I run it, and in 18 levels with a 6 man team I have only seen one death, and it was all three failed saves in one encounter.
Personally I think it is far too trivial to have the counter reset at a short rest. With the amount of healing available to them an adventuring group needs something like this hanging over them to add a little extra element of danger to their day.