Selling is always the hard part. From my experience I think that...

Selling is always the hard part. From my experience I think that you have to consider the following. Has the price rise been too steep because a steep rise often is followed by a fall as people head to the door with a profit in hand. The second thing, is the rise based on speculation or on something more tangible.
When I was a kid Poseidon was all the rage reports of a big nickel find sent this once penny dreadful to $280 a share. The kid next door had a job at disallowed writing the prices of shares on the main board in chalk. Think of that a stock exchange that had teenagers writing prices up in chalk as brokers yelled stuff at them from the pit. My friend bought 2 shares at $240 each.