- Can you submit a paper to a conference that you are not sure you can attend?
- You have agreed to give an invited talk at a conference. But you find yourself traveling too much. Can you cancel your talk?
- You have accepted a tenure-track job at a good school but then you get an offer at a more desirable place? Can you take back your acceptance at the first place?
- You promised to referee a paper by a specific date. But life gets busy. Can you let the deadline slide?
Many members of our community treat such commitments quite seriously but unfortunately too many of us don't. For the latter group put yourself on the other side. Think of the editor dealing with referees who aren't refereeing and the author not getting his paper reviewed in a reasonable amount of time. Think of the department that has stopped their job search believing they have filled their opening. Think of the conference organizers having to reshuffle their program for talks not given.
Sometimes you have extenuating circumstances, like an illness, that do give you reasonable excuse. And you could always ask; people will often modify or let you out of your commitments if you make a polite request. But you must make every effort to honor your commitments. If you don't think you can then you shouldn't commit in the first place.
The ultimate commitment you make is the commitment to research. Once you start graduate school you make a promise to focus on science and your research as your main objectives. Only by keeping that commitment can you truly succeed as a scientist.
How much commitment do you need? In a ham and cheese omelet the chicken and the cow are involved but the pig is committed.