When I was working at Coke, any time a last minute task or request came up, I was the first person to raise my hand and volunteer to stay late and do it. At the time, I thought this was purely a good thing because it showed that I was ambitious and dedicated to the company. And for the most part, it was a good thing. Stepping up like that certainly helped me get noticed, but in doing so, I was unaware of the expectations I was creating by always offering to take on last minute requests.

One evening at about 5 p.m., I was in a meeting with the entire department. My boss had just gotten a directive from the CEO for our team to put together a report that night; he needed it first thing in the morning. This time, instead of asking for a volunteer, my boss just turned to me and asked, “Fran, can you stay late tonight and get the report done?” For a moment, I was flummoxed and unsure how to respond. I suddenly understood I had been too accommodating. By consistently being eager to take on more, I had set a precedent, and now my boss expected me to always be available.

I stayed late and got the report done. It wasn’t the end of the world, but I couldn’t help but feel a little resentful about the situation. Plus, I was concerned about how to handle this situation the next time it happened, as I knew it inevitably would. At something of a loss, I reached out to a mentor in another department at the company and explained my dilemma. Without hesitation she said, “Fran, you need to create boundaries, or people will keep taking advantage of you.”

This was the first time I’d heard the word “boundaries” in a work setting. I explained to my mentor that I wanted to be considerate and helpful and make sure I never came across as lazy or uncooperative. She responded, “I understand that, but if you don’t draw a line in the sand people will walk all over you. Plus, all of your peers are seeing this. If you don’t stand up for yourself, they’ll think they can take advantage of you, too.”

I’d love to say that the next time my boss asked me to complete a last minute work assignment I stood firm and asserted my boundaries. But in truth, it took a few more times for me to decide that I’d had enough. This time, he called me into his office and asked me to stay late that night to write another report. I had practiced what I was going to say in such a situation with my mentor, so I was prepared to respond nicely but firmly while injecting a little humor to lighten a potentially uncomfortable conversation. I said:

“I’ve been struggling with how to talk to you about this. Over the past two weeks I’ve had to change my personal plans three times at the last minute to stay late. I’m afraid my boyfriend is going to break up with me! But truthfully, I wonder if this is a good opportunity for someone else on the team to step up and pitch in.”

My boss was taken aback at first. Then he said, “I’m sorry, Fran, I just assumed. You always volunteer for these things, and I guess I just got used to asking you.”

I already knew I was complicit in creating this dynamic, but it wasn’t until the next week when another last minute task came up that I fully understood how complex this situation really was. This time, my boss gathered the team in the conference room again and asked my colleague Josh to stay late to work on a project. Part of me was relieved, but I admit there was a small part of me that felt overlooked. I automatically feared I was missing out on an opportunity. Be careful what you wish for, right?

In the end, I swallowed that doubt and reminded myself to have confidence in my contributions. There would be plenty more opportunities to take on extra work; I didn’t have to be the one to do it every single time in order to prove my worth. Going forward, my boss was better about spreading these assignments around, and I gradually gained confidence in asserting my boundaries.

I am not trying to discourage you from stepping up and volunteering to take on responsibilities, especially early on in your career when you want to make a good impression. But it is important to look at how you’re being treated compared to your peers. If you’re being asked to “pitch in” or “do a favor” more often than they are, you want to make sure you’re not being taken advantage of.

It’s also critically important to create boundaries at work to help you cut out extraneous tasks so you can focus on the things that matter. Without clear-cut boundaries, it’s so easy to get caught up in the minutiae and let the important things slide, especially if you’re a “nice girl” who wants to please others by never saying no.

Fran Hauser is a long-time media executive, startup investor, celebrated champion of women and girls, and author of the THE MYTH OF THE NICE GIRL (Houghton Mifflin Harcourt, April 2018). She’s held senior positions at some of the world’s largest digital media businesses, including Time Inc.’s PEOPLE, InStyle and Entertainment Weekly as well as AOL and Moviefone. Now an angel investor who largely invests in female founders, Fran was named one of Refinery29’s “6 Most Powerful Women in NYC’s Tech Scene”and Business Insider’s “30 Women In Venture Capital to Watch in 2018.”