This is a big one.
You will need to do alot of listening to get good answers that work for YOU on this one.
My experiences, whether they are releveant to you or not, is for you to decide.
i found that not sleeping because of work worries ended up meaning I was in the wrong job. Changing jobs certainly helped, but there was a deeper problem that needed treating.
It turns out I am clinically depressed. Technically, I have a lower than normal level of a chemical in the brain called Seratonin. This chemical is one of 3 in a coctail that exists in every nerve junction in the brain. It's major function is to be the chemical 'trigger' that is released from one nerve ending, to flow to the next nerve ending across the junction, to trigger firing of that nerve. Without seratonin, nerve impulses are not transmitted propeley.
Seratonin has a short life span. When it breaks down, it inhibits the chemical interchanges in the nerve junctions. So over time your body re-absorbs the seratonin, as well as making fresh seratonin, to keep the nerve junctions primed and ready.
My brain re-absorbed too much seratonin, too fast.
The way this affected me, is that I worried alot, was often stressed, and did not handle additional stress too well. I was prone to rage (without violence) and aggressive re-actions. My quality of sleep was often poor (although it was made worse by sleep apnoea due to massive multi drug resistant tonsilitis that took 4 years to get surgery on), I was intolerant of fools, and erratic.
If this sounds like you, I suggest you bite the bullett and do some of the on-line 'am I depressed' questionairres. You may find a deeper cause than just work.