Married life is predicated on neverending compromise, and at least sometimes, submission to another. Instead of doing what you want most of the time, you have to compromise with another (husband, wife, kids, inlaws, etc.) or outright do what they want. Married life is communal life, and all that comes with it.
Single life is mostly having the ability to do as you please, and as such requires self-reliance, self-sufficiency, commonsense, and an immunity to loneliness. Instead of having to share everything with someone, get their permission/agreement before making decisions, etc., you are independent and free of that.