Would you please correct the mistakes in my sentences. I know that my first sentence doesn't sound natural, but I was unable to write it correctly.

People say that the loneliness of two in a marriage is the worst loneliness. It happens when two people live in a relationship that is dead. The stay together for different reasons. They wait to separate until their children leave school; their are afraid of separation; they hate to live alone; they have debts, or their lack energy to go through divorce proceedings.