If I clearly lost a fistfight with someone, I'd downplay it too when explaining it to my friends, girlfriend, or whatever. I'd have them thinking it was, at a minimum, a draw, while in reality I got the snot beat out of me, despite the fact that I put up a good fight!
Heck, the Japanese were told by their government that they were decisively winning the war against the United States right up to when the Philippines and Okinawa were invaded.
Hitler thought he could force Churchill to sue for peace. Had Chamberlain still been in charge that would have almost certainly happened, but Winston was having none of it. Any way you look at it, Britain beat Germany over the channel. Period.