The Definition Of Perseverance
From a dictionary: "Persisting in or remaining constant to a purpose, idea or task in spite of obstacles." Notice it doesn't start, "Wisely persisting..." Perseverance can clearly be a both a good thing and a bad thing. Remember that when you find yourself wanting to quit something. Quitting might be wisest choice.
Of course, problem with idea that you should quit when something isn't worth effort, is that it's often used as a rationalization. It comes to mind when effort is difficult, but really is worthwhile. It's confusing at times, so how do you wisely persevere? There are three important aspects to consider.
Keys To Wise Perseverance
1. Self awareness: Notice when you look for excuses, rather than truth. Are you letting fear or laziness cause you to quit or procrastinate? If honestly watching yourself is difficult, explain your reasoning to a friend. Close friends may be more likely than you to know when you're rationalizing. (Think about it from other direction and you'll see this can be true.)