First of all, I think it can be great to leave on good terms and have a good reputation, etc. However, I feel like a lot of people blow the importance of this out of proportion, and as a result end up suffering unnecessarily.
I mean realistically, how often is a future-employer going to speak to your manager? It's not like your references have to include your manager, and in my experience it's very rare to have a manager reference as a requirement for a job application. And realistically if a future-employer ever calls your company without you knowing, it would be with HR to confirm employment.