Matthew 24:6 (NKJV)
If you have a problem with a car, and it is not something you can easily fix by yourself, you will have to take it somewhere to fix it. Very often what will happen is that the mechanic will connect your car to a computer that will diagnose the problem to see where the trouble is. It would be foolish to have a car problem and then just randomly try to fix different things without knowing where the actual trouble was in the car. If the engine is not running correctly you would not just change the tires and if you did have a problem with you tires you would not replace the steering wheel.
In Matthew 24 Jesus talked to His disciples about some things that would happen before He returned again. Jesus said that the disciples would hear about wars and rumors of wars. Jesus did not specifically say that the disciples themselves would be in these wars or that they would even be somehow affected by them. But Jesus still told the disciples not to be troubled. Jesus was not telling them there was a physical or even spiritual threat to be dealt with, the trouble would be located somewhere else. Jesus said that things like this would happen but the disciples should not allow these types of things to cause them to be distressed.
Often when we have problems in our life, whether it is something big or small, we will have questions about what to do and even thoughts about what might go wrong or how things might not work out. Even if we are not facing a problem, we could still have similar negative thoughts. This is very much like what Jesus talked to His disciples about, not being troubled in our mind. We do not have to be troubled by things we experience or even hear about. By filling our mind with God's thoughts, His Word, we can successfully deal with wrong thoughts that would trouble us and not allow them to distress us.