Short and sweet since I have never done this before. Long story short i'm getting a better opportunity than where I am currently, but my current employer is kinda bitter about it. The reality is he lives in a bubble of reality he created for himself. I really hate to leave with that kind of situation, but I really don't know what I can do about it. Any advice?<p>EDIT: It's not to say that he was always bitter. He actually is a great guy and does a lot for his people. He is just in a tough spot, and me (as a key person) leaving is really hard on him... and I'm certainly seeing the bitter side of it.
<i>"if you have some useful feedback for your old boss at exit interview, give it"</i><p>I'm not so sure that is good advice.
Your soon to be old boss usually is not prepared to receive "useful feedback". As cathartic as it would feel to tell them that "It would have been nice, even once, to hear you say 'good job' in the 3 years I was working for you." it's unlikely to produce any positive change for you or him. You had X years of employment to share that feedback if you felt it was important.
I'm not sure there is much to do. What do you mean by what can you do, did you have some thoughts about what you think you want to do?<p>As always, when you part way and/or do your exit interview, be professional. Say thanks for the opportunity, that you learned a lot, and answer questions honestly and with tact/compassion.<p>Standard nice things to say when you leave include a) this place is great, but I'm passionate about the new opportunity, and want to give it a shot, b) it's both a great opportunity to do new interesting work and earn more money, c) thanks for all the fish. Temper any negative things you say greatly - if you have some useful feedback for your old boss at exit interview, give it... but don't burn bridges, and don't say anything that's not actionable. Be concrete with any exit feedback... like "I would have liked to have more code reviews from senior developers" is good, but "the code is spaghetti and I hate working on it" is not great.
I don't think there's anything you can do here. This isn't your problem, it's your boss's problem - as a manager, he should understand that employee turnover is an inevitable part of work life, and that managers need to be able to cope with it.