Someone on holiday forces themselves to let-go of all their worries. They reason they have gone to so much trouble, and spent so much money on their holiday that they would be stupid not to enjoy themselves. They would feel a failure if they were not able to relax. With this powerful motivation they force all disturbing thoughts from the mind.
Now take your case: you have been chosen to take the holiday for the whole human species! The onus is on you to take a rest in God on their behalf. Are you going to forego the holiday that the species is relying on you so much to take?