I have an 11 month old son, and we definitely went through this around 8/9 months. He was sleeping through the night and then started waking up again. He had a cold (stuffy/runny nose) at the time, so I didn't let him cry himself back to sleep, since he would end up with a runny nose. But, this then led to us getting up again with him and rocking him to sleep, and I feel like it went on for a month or so. He was teething during this time also - ended up getting 3 teeth at once! And then he might have gone through a growth spurt, because he nursed twice a night for about a week, which he hadn't been doing for a few months. So, I felt like all the sleep training had gone out the window at this point. After we realized that he was waking out of habit and all his issues were over (cold, teething, growth spurt), we decided to let him cry himself to sleep because nothing we were doing was helping. The first night he cried for 15 minutes, the next night 10, the next night 5 and then literally a squeak the 4th night. He sleeps all night again! So, yes, this stage will pass. But, it was a tough one for me! Hyland teething tablets seemed to help him out. Could also be separation anxiety like someone said, because he would also seem to be crying in fear sometimes. I've also heard that babies go through a sleep regression when they are learning new things, and they learn so much around 8/9 months. The stage passed! Hang in there!