I bought $2,000 during the first boom in 2011 - when BTC went from $2 to $30 to $5 in about 6 months.  I bought in around $18 average when it was going down (catching a falling knife) and kicked myself when it went all the way to $5.

Instead of selling at $5 to get some money back, I "wrote off" the money and would check the price every few months or so.  Saw an article in March 2013 about someone selling their house for Bitcoins and figured I would check the price - $66!!!!?! 

Sold half immediately at $67 and sold little bits more on the way up to $140.  I was ecstatic, I had 10% of my original Bitcoins and a handy profit.  But I kicked myself when it kept going up....

Bought and sold a bit quickly a few times (e.g. buy at $150, sell at $170), and my last quick hit almost worked (bought at 188, sold at 25% at $238, $248, $258, $268) the last sell was just $2 over the top.  Wound up getting out at $150 for an overall profit.

Now I just did a quick hit today - buy at $63 - sell at $68.

My best returns are when I put in a little thought and make an immediate buy and future limite sell at one time and walk away - never checking the price.