If we are in the state of fear – worry, about an impending doom, our brain will be showing us the "reality" of what we fear to protect us, so it’s like your computer screen, if you have primarily one website open even though there may be others you wish to see and even are open in the background you’re limited, which is why there is no other way but to eliminate all worry (through trusting in G-d and that all is for the good.)