Insomnia Support Group
Insomnia is a symptom, rather than a disease, and is characterized by inadequate quantity or quality of sleep. People with insomnia complain of difficulty falling or staying asleep, which results in significant impairment of daytime functioning. Insomnia is categorized as transient (shorter than one week), short-term (one to three weeks) or chronic (longer than three...

Fortunately, there is a proven answer -- cognitive restructuring. It's one of the core methods in CBT sleep training. CBT is the gold standard for treating insomnia.
What this method does is give you a strategy for first recognizing these pernicious thoughts, and then nipping them in the bud. You can then replace them with something better, more accurate, more realistic, and more supportive of sleep.
By taking away insomnia's raw fuel, sleep tends to improve. By taking the pressure off yourself, sleep comes more easily.
If you haven't already talked to your doc about using CBT sleep training methods, you might look into it. Also much good info online, including full CBT sleep training programs, if you're the self-help type.