It can be either way. Sometimes a person (for example, a boss) consciously tries to keep someone on their toes. Other times, events -- driving during a snowstorm, for example -- force people to be on their toes.
His wife keeps him on his toes; he's always cooking and cleaning and putting shelves up. She'd call him a lazybones if he didn't!
My new boss keeps us on our toes; we hardly even have time for a coffee break.
That teacher will keep you on your toes; she won't tolerate sloppy work, so make sure you check your spelling and grammar before you hand any work in to her.
His wife keeps him on his toes; he's always cooking and cleaning and putting shelves up. She'd call him a lazybones if he didn't!http://forum.wordreference.com/showthread.php...jemanden / etwas nicht zur Ruhe kommen lassen / in Bewegung halten / antreiben; jemandem ständig neue Arbeit aufbürden
http://www.redensarten-index.de/suche.php?suc...4) von dieser bedeutung, die seit dem vorigen jahrhundert in der technischen sprache ganz ausgestorben, ist die redensart auf der hut sein, in freier verwendung noch übrig, früher auch auf seiner hut stehen, securitati suae prospicere.
http://woerterbuchnetz.de/DWB/?lemid=GH13823