Leaving a long time job is HARD! It is going to feel like you are leaving behind friends and 'family-type' people. you grow attached and comfortable.... Ive left many jobs, Im a job hopper bc I work in computer/hi-tech, so I go where the money and jobs are when mine gets stagnant! Trust me that you are doing the right thing at this point... the sadness will pass and you'll be excited to grow and expand to your full potential!
Good Luck with your new endeavor!!