Every time you commit to something new, you not only commit to doing the work itself, but also to remembering to do the work, dealing with the administrative overhead and to getting it all done in the time constraints involved.

The best way to break out of the vicious cycle of overcommitment and underperformance is to very carefully manage what you agree to do.

You can actually do more if you take on less.

Here are a few steps you can take to prevent overloading your plate:

Create a pause. Whenever possible, avoid agreeing to new commitments on the spot. Instead, slow down the decision-making process to give yourself the space to make a reasoned choice.

First, ask clarifying questions. For example, if someone requests that you take on a presentation, say, “That sounds interesting. What did you have in mind?” Ascertain how much prep work it will require. Then, ask for some time to review your commitments and get back to them with an answer: “I’ll need some time to review my current commitments. Would it be reasonable for me to get back to you tomorrow?” People want to be “reasonable” so they’ll typically say “yes”.

Say “no” early and often. If you immediately know that you don’t have the capacity to take on a project, say “no” as soon as possible. The longer you wait, the harder it will be for you to decline the request and the more frustrated the other person will be when they receive your reply. A simple, “This sounds amazing, but unfortunately I’m already at capacity right now” can suffice.

Think through the project. If you want to take on the project, stop to think through what you’d need to do to complete it. For a presentation, that might include talking to key stakeholders, doing research, putting together the slide deck and rehearsing. For a much larger project, the commitment may be more extensive and less clear.

Map out what you know and then make rough estimates of the amount of time you think the steps might take.

Review your calendar. Once you’ve thought through the commitment, review your diary. This allows you to see where you have – or don’t have – open space in your schedule. In the case of the presentation, if you see that your calendar has open time, you can commit to the project with confidence and block out time for it on your schedule.

If your calendar has no time free between now and the day of the event, and the presentation would require prep, you have a few options. The first is to simply decline, based on the fact that you don’t have any available time in your schedule to take on anything new. The second option would be to consider renegotiating your current commitments so that you could take on the new project.

Adjust your commitments. If you take on something new that will impact other projects, make people aware of what they can or can’t expect from you. They may not prefer that you made another initiative a priority, but if you’re aligned with your boss and your goals, you’re making the right choice.

Also, if you let people know what to expect as soon as possible, they're less likely to be upset. This gives you the opportunity to work with them on creating a new timeline or on delegating work to someone else with more availability. – Copyright Harvard Business Review 2015 Elizabeth Grace Saunders is author of How to Invest Your Time Like Money.