Babies' Sleep is Not Linear.
The one thing I wish all new parents knew is this: babies' sleep isn't linear. So many people (myself included) have an impression before their baby arrives that sleep will start off horrendous, and then gradually improve until baby is sleeping through the night. In their own room. At six months old. (If you have a baby over six months old, I imagine you are wryly smiling right now.)
For some babies, that magical "sleeping through the night" does come that early. But for many, many more - the vast majority of babies in fact - that moment will come a lot further down the line. And the journey there will have bumps, and loops, and roadblocks.
So many parents, not having this information, think that there is something wrong when baby's sleep seems to go downhill. They think they need to do something drastic to fix things.
The absolutely hardest time with my own son's sleep was 8-11 months. If you'd told me that before he was born, I'm not sure I would have believed you. But it's normal. So normal.
There are ways to support yourself, and your baby, through these normal developmental phases without taking drastic action to interfere with your child's natural, biologically normal and developmentally appropriate behaviour.