Why can't I sleep at night...?

you pretty much answered your own question here... any stress/negative thoughts/depression can cause temporary insomnia. try not to think about your stressors before bed... fall asleep to a movie or listen to music or read a good book. there are things that you can control and things you cannot control and you certainly cannot control anything laying in your bed thinking about things. they'll wait until the next day or whenever it is that you can take care of them.

Relax, try not to have things on your mind.....Be clear from thoughts or if you think about things, think pleasent thoughts, you will then fall asleep.....If you dont fall asleep after laying down for awhile, then get up, drink something then try it again, usually works...

It is definitely anxiety. Lots of those thoughts can come from depression, too. Maybe you need to see a therapist if not medication, also.

Could be temporary issues of everyday life. If it's been going on for awhile...maybe it's anxiety or depression....it's treatable.

drink hot milk and do exercise before sleep.

Go have sex with hot chicks and after that you will be so tired you will fall asleep and sleep well.