When you imagine everything going wrong , find yourself catastrophising a lot and creating mental fantasies about future events turning out badly, this just makes you feel anxious and panicky and ill equipped to deal with every day life.

On one level you might even know that you are being irrational and that these things wont probably happen but that does not stop the emotional part of your mind cycling through the same old worry thoughts, over and over.
When you vividly imagine everything going wrong, your brain and body start behaving as if those things were actually happenning. Your heart rate increases, adrenaline is produced and your body gets ready to fight what it believes is a real and present danger. but of course the future threat you are imagining happening is all a mental fantasy and you are actually just at home in your sitting room, scaring yourself with imaginary scenarios.
Being able to imagine how the future will be is a huge help when you want to set goals and work towards bettering yourself and deciding what you will do if things go wrong are all part of effective planning. it is foolish to believe everything will go to plan though and ups and downs are all part of lifes package. Sometimes a flight will be delayed or it will rain on a brides wedding day, these things are out of our control.
But when you focus too much on things going wrong, you end up distorting reality and cloud your ability to think clearly. it is rare for things to go terribly wrong and its just as rare for things to go absolutley perfectly right all the time. Most of life happens in the middle of the two extremes.
A more balanced and rational way of thinking about things becomes easier when you know how to calm yourself down and realise that you have been at the mercy of your own thoughts. You learn to take command of yourself and to deliberately calm and quieten your mind. There are many Hypnosis techniques that you can learn to calm down that anxious part of you, so that you can think clearly and rationally about things instead of going off at the deep end when things do not always go to plan.