A couple had just got into bed upstairs when the wife asked, "Did you switch the kitchen light off?" "Yes Dear," he replied, but minutes later he said, "I'd better go down and make sure"!
Unintentionally she had sown a doubt but Satan loves to do this! When God warned Adam and Eve, that they would surely die if they ate the forbidden fruit, Satan said, "You will not surely die!" [Genesis chapter 3].
The Bible says, "Resist the devil and he will flee from you." [James ch 4 v 7]. So let's say emphatically, Heaven and Hell are real and Jesus is the only Saviour. Let's doubt our doubts, believe God's Word and Satan will flee!