Selling along the way is actually what most people do, in fact very few people hold to precisely sell at ATH. In theory it all sounds easy - buy/sell with portions, buy the dip, sell the tip and so on, but on practice everything is hard. But I agree with you that not being too greedy is one of the important skills in trading.
Ps. Also remember to spend at least 20% of all the coins you buy, to feed the merchant network and use case for Bitcoin, or it will die as a currency.
I will start using BTC as a currency when I'll be able to buy products that I buy and at competitive prices.