The word "ambition" conjures up thoughts of lofty goals. Children are always taught to have high aspirations for themselves. "Don't settle for second best" or "If you're going to dream, why not dream BIG?" are things they hear. Some have the ambition to be President or a superstar athlete. Ambition is good for self-esteem, as long as it is kept in check and the goal one aspires to is godly and wholesome.
Christians have read and heard taught countless times Jesus' statement to Pilate in Jn. 18:36..."My kingdom is not of this world." We have pondered on numerous occasions Paul's admonition in Col. 3:2..."Set your mind on things above, not on things on the earth." There is no greater challenge to N.T. Christianity today than worldliness. Parents should teach their children daily the dangers of conforming because young minds are barraged constantly (cp. Rom. 12:2). We teach them to be ambitious and at the same time to consciously "go against the grain" of the world. It can be confusing to them. They sometimes question, "Does God really want us to not live like the world?" The answer, of course, is a resounding "YES" and can be proven by something Paul says in 1 Thess. 4:11a.
The KJV doesn't really convey the idea as well as the NKJV or NASV. The KJV translates it "...study to be quiet..." The NKJV has "...that you also aspire to lead a quiet life" while the NASV has "...to make it your ambition to lead a quiet life." It takes a spiritual mind to fully understand the concept that living a quiet life is an "ambition." The Greek verb is defined as "to be ambitious; to strive earnestly, make it one's aim." It may seem contradictory to aspire to a "regular life." This is the challenge to young people or those who adopt a worldly mindset (cp. 1 Cor. 2:14). Yet, the paradox disappears to those who love the Lord and want to do His will.
Ambition for worldly things is grounded in immediate satisfaction. Go for the gold NOW. Ambition for eternal things requires patience for a FUTURE reward. Thus, Paul's exhortation to mind our own business and labor that we lack nothing (1 Thess. 4:11b-12).
Truth be told, there can be no higher aspiration or ambition than heaven. How much better can it get? If that's your ambition, your goal is admirable. If not, you're simply wasting your time.