What effect does IBS have on one's lifestyle?

Variable. Constipation predominant IBS is usually fairly well tolerated. Nuisance level. It can be more severe with chronic discomfort. Combined IBS with alternating constipation and diarrhea can be more troublesome as it is less predictable. It should not interfere with sleep. If it does it may be due to dietary intolerance or perhaps inflammatory bowel disease.
Depends if. You let it take control of your life. Eat healthy, hi fiber, regular mealtimes and frequency, and drink plenty of caffeine free, alcohol free fluids daily and you will control the symptoms, rather than the symptoms controlling or affecting you.