Not sure if anyones asked this or not, didn't notice it. Are you able to stand up and pedal or are you doing it all sitting down?
I also didn't notice if you answered the question about what bike and gearing you had.
Also is it a new bike or one thats been sat in the shed for a little too long? It may need a bit of TLC, bit of grease here and there, little spot of oil where it counts and the right amount of air in the tyres can work wonders!
I, as a number of others here seem to prefer, don't look at the top of the hill, I just concentrate far enough ahead that I'm not going to crash into anything, although I can't resist stealing the odd glance now and again, the top is always further away than I thought it would be! As for a mantra, I'm not aware of one but I suspect it's something like "Please make it stop, my legs are burning!" repeated over and over again with increasing desperation.