Knowing I have to get up, that I'm likely to be disturbed early, or that I'm needed at a particular time in the morning makes falling asleep really hard. That and I find it a lot easier if I'm on my own with no-one in my space or interrupting me or chatting or asking for stuff or anything as I'm winding down and relaxing in the ~1hr before sleep. And that's before you throw in any extra actual life stress on top of fairly-normal things like having to be up at a certain time or having a partner.

... so yeah, as a married guy with kids and a job, falling asleep is hell basically every night.