When you hear about setting boundaries, you probably think of toxic family dynamics or people pleasers who unwittingly become their friends' doormats. But as an entrepreneur, you probably let your personal boundaries get trampled every single day without realizing it.

Maybe you agree to look over a colleague's business proposal. You shrug when you're named chairperson of the committee. You push back your own scheduled head-down work time to help an employee solve a problem. Or you utter an "OK" when you're appointed to another startup's board because you can't think of a reason to say no.

These moves all make you a great mentor. But they also disregard the boundaries you need to set to get your own work done. And the problem is that once a boundary has been crossed, it will likely be crossed again -- unless you change the dynamic.

Why You Need to Be a Better Boundary Setter

These demands on your time sound little, taken individually. But remember that you have the same 24 hours in a day as everyone else. If you siphon off five hours here, three hours there, another couple hours there, you eventually have very little time left to devote to your own goals. If your goal is to leave a legacy as an entrepreneur who built up other leaders, that's fine. Assuming you want to build a successful business of your own, that won't work.

Beyond that, you're setting an example for your team. High achievers will take note that you're sacrificing yourself to help others. They'll make one of two assumptions: They need to sacrifice their own work well-being when others need help, or that they need to work long hours to get both their work and everyone else's done. That will lead to either burnout or work interruptions, neither of which is a good long-term strategy for your company.

How to Set Reasonable Boundaries

This isn't a call to arms to refuse any request that comes your way. There are times when sitting on a board or solving an urgent problem with a co-worker actually is in your best interests. The trick is to identify how your time is best spent.

1. Question your motives. 

Are you about to say yes to that request because you genuinely want to do it or because you want this person to like you? Do you see a financial payoff down the road? Do you think this will help grow your business? Do you see the potential for a partnership?

Get real with yourself about why your knee-jerk reaction is to agree. If you're simply boosting your ego or distracting yourself from something harder you don't want to address, that deserves a no.

2. Lay out your calendar. 

One tricky issue with not scheduling everything you want to do is that it gives the illusion of free time. If you don't schedule a date night or a workout session, it's like it didn't happen -- or never will. After all, if 2 to 3 p.m. appears open on your calendar, you're likely to accept a meeting with someone in your network.

You may actually benefit more from a meditation session or a brainstorm with your co-founder. Write down everything you need to do so you know where real gaps exist.

3. Think of the ripple effect. 

Everything comes with an opportunity cost. If you agree to take that board position, does that mean you'll miss your kids' athletic events? Helping one co-worker may mean you can't help another. Will your spouse resent you being gone an additional 10 hours a month for that nonprofit? Think about the tradeoff of any choice you might make -- that can stop even the easiest yes from slipping off your lips.

4. Predict boredom and fatigue. 

One thing I like to do when I feel like I might be taking on too much is look to the future. If I take on every single thing I'm considering, what's most likely to make me feel tired or bored later on? It's crazy how quickly this line of thinking gets me to pinpoint the opportunity I'm least excited about. It's how I saved myself from a mastermind group, a speaking gig and mentoring opportunity that I knew wouldn't be right for me.

Being a leader with multiple intriguing opportunities at your feet is a nice problem to have. But you'll create much gnarlier problems for yourself if you don't learn to determine what really deserves your time. Saying yes can bring you short-term gains and long-term headaches. Before you agree to something you're not 100 percent sure of, take these steps. You'll thank yourself later.