For every share sold, a share is purchased. So, it's clear, the psychology of fear and/or greed determine the stocks direction. With an IPO, you have extreme volatility, which is a traders dream, knowing you have to be in it to win it. This massive buy-in drives the stock up followed by spikes down as traders sell off their quick gains. In time however, the stock will settle down as traders move out of the stock and move on to more volatile stocks.
The price held at $35 reflecting an equal push pull between those who want the stock and those that wanted to take profits or cut their losses. The volume at the end of the last hour was classic to this dynamic, and the fact that the major volume was accumulation (ended in the green per volume spike based on the minute interval it occurred), technically means we're due for a bounce.