How and when does imagination overcome reason and fear?

E. g. When a child is afraid of scary monsters under his/her bed, he can imagine the good and happy heroes that will fight and defeat the scary monsters. This overcomes fear.

Another form of imagination to overcome reason is hope. E. g. A person hopes that one day he will recover and be able to walk again despite doctors saying he will never walk again. That hope/determination makes one never give up trying till one walks again. Therefore such an imagination is determination to overcome scientific reasoning.