It will be a mixture of both, but trying to analyse why will not help you sleep. I hardly slept at all for 2 or 3 nights after ASBO died.
1. Do not get stressed about it, it's normal. Your body will eventually say "enough" and you will start sleeping.
2. It's ok and normal to feel like ***.
3. Sit or lay down somewhere comfortable, then start your brain thinking of something of no consequence (my favourite thing is to think about one of my family history brick walls - it's terribly repetitive and boring and generally I'll nod off).
4. If you don't nod off, don't get stressed about it. Accept it's *** cos it is but know that this too shall pass.