I know that what works for me on bad nap days is to put my LOs down for bed a little earlier. Especially for my 2 year old. If he doesn't get a long enough nap, he starts to melt down earlier in the evening. I go with that, and put him to bed. (usually about a half hour earlier, or so.) It seems to help him sleep thru the night. If I keep him up for regular bedtime, he gets overtired and will wake up in the middle of the night or blazingly early the next day. I read somewhere that earlier bedtimes lead to later wakeup times anyways.
I also try to heed this with my 12 week old, who is still struggling with the 40 minute nap monster. If we don't get enough of those in, I let him crash out earlier at bedtime to avoid getting overtired. It seems to work for me... Good luck. I know how that is, I've been there.