It will pass, but you need to be really consistent with saying no & sitting him back down. When he sits for a bit, praise praise praise!!! I'm sure for several months all you could hear in my bathroom was "Sit down Zander. Good boy, that's wonderful sitting, excellent work. No Zander sit down, you'll slip over.... Good boy sitting nicely, good job." LOL! Make sure you explain to him why he needs to sit as well, he will understand a lot more than you think