Scripture says, "Therefore, encourage one another, and build up one another..." (1 Thess. 5:11, NASV). Acts 11:23 records Barnabas as coming to Antioch "and encouraged them all that with purpose of heart they should continue with the Lord. For he was a good man..."
Whenever I think about these things my mind always goes back to the Old Testament, to the children of Israel while they were in the wilderness. Their murmuring and complaining was almost constant. And, it is important to observe, God was sorely displeased with them. You can read about it, with much profit, in Numbers.
But this is not just an Old Testament wilderness problem. Jesus was on the receiving end of much complaining. John 6:41 says, "The Jews then complained about Him..." His response was immediate, instructive, easily understandable and practical to do. "Do not murmur..." (John 6:43). The New King James footnotes this with a simple, straight forward, alternative translation, "Stop grumbling."
The Holy Spirit moved Jude to write about it with blistering, sharp, rebuking words. "Behold, the Lord comes... to execute judgment on all, to convict all who are ungodly among them of all their ungodly deeds which they have committed in an ungodly way, and of all the harsh things which ungodly sinners have spoken against Him. These are grumblers, complainers..." (Jude 14-16).
Of all people, God's people ought to be the least ready to complain and murmur, yet it is evident we are not. We possess the greatest blessings and hope and yet we often go through life fussing, complaining, griping, finding fault with so many things. James 3:10 is appropriate. "My brethren, these things ought not to be so." Note the context of this verse is discussing the misuse of the tongue!
Why are we this way? Carelessness and thoughtlessness are easy answers. It is easy to find fault, to pick at things, events, people, and yes, brothers and sisters in Christ. A negative, critical attitude can develop within us before we know it. It becomes habitual, addictive and unrecognized by the complainer because it seems so natural. But, it is inexcusable and unacceptable. It is sinful!!
How can we stop? Jesus told us. Just stop it! "Stop grumbling." A practical suggestion. Make it your rule to speak two commending things BEFORE speaking one complaint. If you cannot, then don't complain!!