Sometimes I have to walk halfway up this one hill on my ride home. I make it more often than not, but my lung capacity (that's what gets me, not legs, I run out of breath) isn't enough due to a few pulmonary embolisms that I am in recovery from.
That said, if you don't want to change your gearing, then I say go as hard as you can, as far as you can, and then you'll be able to do it. I know that more than half of it is mental. If I am coming up on the hill, telling myself I can't do it, odds are, I can't do it. But, if I am mentally tough and refuse to quit, then I make it at 10ish mph.