I spent this summer in Baltimore, which is basically at sea level. By the end of the summer, I was able to run 9 miles at a 7-something pace (and still have more left in the tank). Before this summer (all spent in NY), the longest I'd ever run was 4 miles. Fast forward to now: Im back in NY, and I'm struggling to run 1 mile at a 7 minute pace. This is 2 weeks removed from running those 9 miles. The elevation here is a little over 1,000 feet above sea level. Is it possible that 1,000 feet means this much difference, or am I simply psychologically beaten?