<<Why don't you just simply take a "good" tax loss>>
I always sell a loser before it turns into a 1-year loser. Even in my tax deferred and tax exempt accounts. It did not work out, it is a piece of paper, get rid of it. What looks best now? Something you lost money on? Unlikely.
If you rode NRGY all the way down, do some research before selling at what could be near bottom. Don't look at your basis. Look at NRGY's potential upside versus alternative equity choices. If you think NRGY has 20% upside with a likely 5% dividend, do you have another stock with that potential upside? What is your conviction level and your risk level on both stocks? If you can take a tax loss, it's probably best to sell; in an IRA, you need to make a careful decision because you are taking the full loss. I hate selling losers in an IRA; but I really hate seeing losers sitting there as dead money for a year or more.
"If you can take a tax loss, it's probably best to sell;"
Be careful with that for an MLP in a taxable account. You may have a capital loss but also significant recapture of distributions at ordinary income rates if you have held a number of years. People selling for a tax loss may find that they actually end up owing tax on the sale.