Life after pregnancy- newborns- the 4th trimester

I've recently heard about "the fourth trimester" which is basically the newborn stage. To listen to women talk about life with a newborn, it honestly sounds dreadful and depressing with the lack of sleep, constant pain, and over all lack of mobility. It scares me. I'm prepaired for discomfort and less sleep but man they make it sound like the end of the world sometimes! This will be my first child so I don't truly know what to expect so I'm here to ask, is it really that bad?? Will I be miserable?