Almost anything is easier to get into than to get out of. Authority tends to assign jobs to those least able to do them. Celibacy is not hereditary. The one friend or relative for whom you didn't buy a gift will arrive with one for you. The toughest thing in business is minding your own.
Opportunity always knocks at the least opportune moment.
An expert is a person who avoids the small errors while sweeping on to the grand fallacy. There ain't no such thing as a free lunch. Any system which relies on human reliability is unreliable. When all else fails, read the instructions. The person you're most attracted to never shows up until the day before the vacation ends.