I wrote an article a little while ago on getting big yields from ETFs (exchange-traded funds). One ETF I mentioned was iShares Dow Jones Select Dividend Index (AMEX:DVY), with top-25 holdings that include Comerica (NYSE:CMA), Kinder Morgan (NYSE:KMI), Chevron (NYSE:CVX), Unitrin (NYSE:UTR), KeyCorp (NYSE:KEY), and Lincoln National (NYSE:LNC). I mentioned some favorable things about it and also offered a caution or two.

As often happens, I heard from a few readers regarding the article. One reader, Dave, said: "I'm totally retired, and my wife is still working at age 65 and investing in her 401(k). We both have an IRA with Fidelity and were among the first to buy DVY when it came out. Both of us had significant holdings in DVY after it came out until the end of last year. Until the last four to six months, we were very pleased with DVY, with its ability to beat the S&P 500 yearly growth and, of course, the dividends. That changed last year, and the performance and dividends went down."

He continued: "We liquidated all of my wife's DVY in her IRA and bought Fidelity Strategic Dividend & Income Fund (FSDIX), which outperformed DVY significantly . I sold 70% of my shares and bought income-producing ETFs."

I'm torn when I read things like this. On the one hand, it's very important and good to keep up with your investments, to see how they're doing, to compare them with alternative investments, and so on. Not enough people do so, and Dave is to be commended for it. That said, though, I think he's being hasty in dumping a holding if his main reason was that he didn't like its performance over a short period of time.

In the long run, we obviously want our holdings to go up in value. In the short run, though, anything can happen. Good stocks and good funds can falter. Sometimes, if a holding falls and you still have great faith in its long-term prospects, the fall can be a good opportunity to snap up a few more shares.

If Dave's rationale for selling was that he didn't like changes he saw in the management of the security (such as its becoming less concentrated), then that would strike me as much more valid.

When it comes to selling any holding, don't succumb to your knee-jerk reactions. Think the situation out carefully. Here are some enlightening articles on selling:

Meanwhile, if you're looking for investments that will kick out income to you, I invite you to take advantage of a free trial of our Income Investor newsletter -- That way, you'll be able to see the entire list of recommended investments and how they've fared, as well as gain access to all past issues and special reports. Not a bad deal for free, eh?

Finally, you can learn a lot more about ETFs in our ETF Center. Click in to learn how ETFs stack up against mutual funds, how to develop an investment strategy with ETFs, pitfalls to avoid, how to avoid the ETF imposters out there, and more. These articles may also be of interest:

Longtime Fool contributor Selena Maranjian does not own shares of any companies mentioned in this article.