My boss told me that he wants me to switch projects soon and I am not sure how to feel about.

Old project
- have been working on it for four years, mostly alone, sometimes with others
- i am more or less product owner and make most of the technical decisions
- i assign tickets to other when they get assigned to help me
- i inherited the code base and refactored a lot. Some parts i am proud of, others are a mess and others aren't touched by me at all
- one of my helpers would take this

New project
- kind of data science plattform, so I have to learn a lot in this direction. Will be very complicated though.
- my first big greenfield project actually
- i will be mostly alone with this
- tech stack is fixed; no more php.