While one should always be vigilant at looking for opportunities, sometimes there are none and that sticking to your existing portfolio is the best thing you can do.
In order for any investment to be successful, you need to make two critical decisions. The decision to buy, and the decision to sell. If you get the buy correct, but ruin it by an incorrect sell decision, the results are quite depressing. Just look at those people that bought Apple at $50/share and thought it topped out at $100. Sometimes those decisions are good – if you dumped RIMM at $60 a couple years ago, you’d be laughing.
Traditionally in my own investment history, my entries have been quite good, but most of my sell decisions have been early to the game. I have been trying to improve this.