Dear Prudence: I am a hormonal young woman and was craving an easy hookup, so I tempted fate on the Internet. Of the hundreds of responses I received, one stood out because he accidentally attached a professional summary. I found out it was a man who works in my field, and is a fair number of years my senior. We met up; we hooked up; we became friends. He and I are both unmarried and unattached, but neither of us wants to have a romantic relationship with the other. I have now begun to date closer to my age group, so I don't want to share playtime with him anymore, but haven't told him yet.

Being entry level in the field, I could really use a mentor and have excellent access to this guy. I really don't want to exploit him or make him feel rejected or awkward, and I want to be as professional as possible to keep suspicions of "secret lovers" at bay. Two questions: 1) Is it OK to pursue his help with my career, maybe in a formal informational interview or by asking for introductions? And 2) How do I go about this tactfully? Connect with him on LinkedIn and send a formal e-mail to his work address?

Prudence says: I can just hear the kind of glowing recommendation your hookup can give you: "Juliette has a wide-ranging skill set. She's always ready for action and throws herself passionately into any task. She has the flexibility to be considered for a variety of positions."

You have a rather naive idea of what a mentor is and how you get one. Facebook COO Sheryl Sandberg, in her book "Lean In," says she hates when young women, some she barely knows, ask if she will be their mentor, the way little girls ask each other to be best friends. She writes of women your age: "We need to stop telling them, 'Get a mentor and you will excel,' Instead we need to tell them, 'Excel and you will get a mentor.' "

You have excelled with this older man, all right, but not in a way that he can convey to his colleagues. Sure, you selected him to relieve your urges not just because of his personal skills but also his professional ones. Given that, it would have been fine for you to have engaged in a little pillow talk about your mutual vocation. But now that you want your assignations to be done, you can't expect he'll welcome your showing up on his work networks or at his office. He knows you as someone who's on the make, but in the wrong context.

However, since you say you two have become friends, you should meet him for drinks and explain that while you've really enjoyed your adventures, you're looking for something more permanent with someone your own age. Then say you'd like to stay in touch. If he agrees, when you get together for lunch, at some point ask his advice on how to move up in your field. For the future, keep in mind it's better not to look for a mentor when you're both out moonlighting.

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