DS is 9 months tomorrow and in the last few weeks has learnt to stand up and so everytime he wakes up (or we try to put him down for a nap) he pulls himself up. He doesn't seem to know how to let himself down so you then need to go back in and lay him down. He then screams and stands up again and the cycle is usually repeated a about 20 times. Anyone have any tips on how to resolve?