Really difficult to sleep in the night. feeling kind of anxious but don't know why and this prevents from falling asleep. and happens only at night?

Initial Insomnia.: When some people lie down to sleep and there are no distractions, they begin to ruminate. The more they ruminate, the more anxious they feel & the more they stimulate their brain. The brain needs to slow down for you to sleep. Buspar (buspirone) sometimes helps someone to be calm at that time just before sleep. Consider deep breathing exercises, meditation or progressive muscle relaxation.