DON'T USE WHAT YOU HAVE NOT TESTED

JUST THINKING:

Pilots are professionals who have gone through various trainings and examinations. Before a person is licensed to pilot a commercial plane and putting the lives of passengers in his hands, he must have been tested, certified fit and competent to do it. This is the proper thing to do in life but many people cut corners and it leads to disasters. Please, do not use anything you have not tested, tried and proven that it is working optimally or else you will expose yourself unnecessarily?
I Samuel 17:38-39 NKJV, "So Saul clothed David with his armor, and he put a bronze helmet on his head; he also clothed him with a coat of mail. David fastened his sword to his armor and tried to walk, for he had not tested them. And David said to Saul, “I cannot walk with these, for I have not tested them.” So David took them off". 
David could not walk because of the armour he was putting on. But when he took them off and put on what he had tested, he moved or drew near Goliath. He was not used to the armour but he was used to the stones, shepherd’s bag, pouch and  the sling. He was in his comfort zone using those items. However, he was out of it (his comfort zone) when he had the armour on.   
This thought contradicts what we have been told and taught that we need to challenge ourselves and move out of our comfort zone if we want to be successful. But one thing I learnt from David's comfort zone is that you can do well in your comfort zone. Also, it will take time to adjust to the new zone, using something new and using something you have not tested. 
David would have gotten used to the armour if he kept using it daily. So, the usage of a thing makes you proficient in it. If you keep using a computer system daily, you will become more confident with it. This means that a new zone or a new project could be for a long time but the comfort zone meets the immediate challenge. Both the comfort zone and the new venture are very important. Do not neglect either of them.
A medical Doctor will not prescribe drugs to a patient that has not been tested, proven and not trusted. A car dealer except dubious ones will not sell a car that he does not have knowledge of. No true professional will recommend anything he has not tested and proven. A tested thing is something you use daily easily and you can navigate your way around and with it, you can vouch for its usefulness, integrity and duration. While a trusted person is one you have walked with, worked with and even lived with over time and you can vouch for the person's competence, integrity and so on at any given time.
In leadership, this is what is obtainable. When an organization wants to pick a leader, they will pick someone who has been tried and tested in every area and he proves that he is capable. In a football team, a coach will always play the players he has faith in as a result of the series of trainings and the testing of his players’ capabilities, strength and skills. Even the bible states that you should not use a rookie or a new convert as a leader (1 Timothy 3:6).