In The Dip, Seth Godin offers a great primer on strategic quitting. He  explains the difference between "dips," something really difficult but with the opportunity to be the best in the world on the other side, and "cul-de-sacs," where continued time and effort leads you right back to the same spot.During my seven-plus years as a full-time entrepreneur, I've navigated quite a few professional dips and cul-de-sacs both for myself and with my time coaching clients. In this journey, I've discovered some of the most common cul-de-sacs that can trap creative professionals.

Here's how to identify when quitting is the winning option:

If it's supposed to be fun, but it's not

Getting started—even on things you really want to do—can require a huge amount of effort. But if it's the right investment of your time, you usually end up enjoying the process, feeling accomplished when you're done, or at least appreciating the results. However, if you keep at an optional activity for a month or more and don't experience any reward for your efforts, it may be time to call it quits. Just because you started something, doesn't mean you have to finish it, especially when you took it on primarily as a source of fun and pleasure.

For Example: Stop attending classes, going to events, or practicing skills where you dread beginning them and at the end of doing them, you wish you hadn't.

If more effort produces little value

If you've extracted the value you needed from a particular pursuit, spending additional energy on it can waste your time. In other words: the law of diminishing returns.
For Example: If you read what you needed to from a book or an article to complete the project at hand, you don't need to pressure yourself to finish reading the rest simply because someone wrote it.

Stop practicing skills where you dread beginning them and at the end of doing them, you wish you hadn't.

If short-term gains lead to long-term pains

Sometimes you need to go the extra mile and push yourself to the next level of achievement (the equivalent of some muscle soreness after a strenuous work out). But when your strivings lead to debilitating consequences, you'll want to pull back to avoid burnout (the equivalent of serious, potentially life-long injury).

For Example: If you start to experience extreme physical consequences as a result of trying to complete a particular project, you may need to slow the pace or stop the work. Red flags of acute stress reaction include sleeplessness, constricted throat, agitation, depression, and panic anxiety.

If it's no longer the most important task or project

Moment by moment, you need to make decisions about what's most important now. In a perfectly controlled environment, you could decide on your priority, execute, and then move on to the next item. When completing your current project puts you at risk of not doing or completing something that's now more important, you should stop or delay the previous item.