Articulation is critical here.
Try making a slight crescendo as a phrase moves up, and a decrescendo as it goes down. For a little variety, experiment with doing it the opposite way. This strategy may help you to practice this at first, but you should start thinking in quarter-note beats as soon as possible. I've recorded it at about that tempo, though I think you could play it as fast as 54 or so to the quarter note before it gets too fast. The trill in m. 13 is the only technically tricky spot.