You have just dropped the bombshell news on your boss that you are leaving. After they pick themselves up off the floor, there will usually be one of three reactions:

1. Congratulations, good for you!
2. Traitor! Pack your stuff and get out (or work through your notice and endure my constant looks of contempt)
3. Sorry to hear that, is there anything we can do to keep you here?

1 is the best outcome, 2 is not comfortable but you are a grown up and can deal with immature people. 3 is the worst. It means that they are not accepting your resignation and think that this is just an invitation to negotiate.

When you resign you need to say unequivocally that you thought long and hard about this new opportunity and you ARE taking it and you ARE leaving. No ambiguity, no mincing of words and no backpedaling! If the boss still throws option #3 at you, you must make it clear that your decision is final and you would not entertain a counter offer. If you don't do that, that will create the opportunity for them to guilt you into staying. If you are thinking of opening the door to a counter offer, think about these points then decide if you want to listen to what they have to say. I would be amazed if you could.

• You looked elsewhere for a reason, will whatever they counter with (money, promotion, etc.) really make you happy and satisfied with your career?
• Are you going to have to find another job and threaten to quit every time you feel you deserve a raise or some other recognition?
• You have let it be known that you were looking elsewhere, they know you are a flight risk and are going to try and keep you around until they find a replacement
• The great majority of people who accept counteroffers are not working at that job 6 months after accepting the counter offer (either voluntarily or not)
• You accepted another offer somewhere else and now have to go back and retract your acceptance. Are you ready to burn that bridge? More than likely if you try to go back after rescinding your acceptance you will be turned away. You have revealed a character flaw and there's no putting that genie back in the bottle

Just some things to think about. Like ending any relationship, or pulling off a band-aid, you need to get through some initial discomfort. This will quickly pass and you will see that you did the right thing. Just remember why you did all this and that will keep you guided in the right direction when confronted with the counter offer discussions.