The word “wait” by itself means to stop moving for a while. Starting around the mid-1800s, “wait on” was used to indicate serving. Isaiah 40:31 (KJV), But they that wait upon the Lord shall renew their strength. (MSG) But those who wait upon God get fresh strength. It is better to wait (serve) while waiting (idle). Paul warned the early Christians against simply waiting for the Lord (2 Thessalonians 3:10-11).  If one is able but unwilling to work to provide for himself or his family, it is unjust for him to receive the necessities of life provided free by those who willingly work. 

Everything in the universe takes the path of least resistance. Water, electricity, and even people. I have found that the more I wait to do something, the harder it is to eventually do it.  We have heard the idiom "A watched pot never boils." That is because many people, and especially those with some kind of hyperactivity disorder, just cannot wait. They have to be doing something. Why not, while waiting on God for an answer about one thing, wait on (serve) God in something else? That way, you never stop serving God while your heart and mind catch up.