At my company my boss is the CTO of the company. When I was first hired I was super excited and grateful for the job and was ready to do anything. This is my third job out of university, and my first job where I am actually not treated as a slave, and am treated as a human being.
He has asked me at one point to work on a side project for something that he wanted. It is nothing big or relevant to my interests, but at the moment I was on the 7th cloud from being hired so I decided to happily accept. Now this is a project for which I am not getting paid for and am asked to do on my spare time at home. I signed some papers stating that I will keep the project a complete secret and not tell about it anyone at work, and not show the code to anyone.
Fast forward 8 months later, I still love the job I do at work, but the side project is not fun at all whatsoever. I am slowly becoming an adult, and want to start a family and also would like to buy a house. So now not only is this project not interesting to me, but I have absolutely no time or desire or interest to work on it. Even if I had the free time, I still have no desire to work on it because it is not the type of programming I would like to do on my spare time. And I simply made a grave mistake for saying that I will try working on it. I wouldn't want to work on that project even if I was paid double of what I am being paid right now to continue on it. That pretty much sums up how much I want out. And if I go out, then the whole thing will have to be scrapped and restarted. The project itself will of course be a long ongoing thing even after I finish working on it.
How do I gracefully tell him that I do not want to work on this project without causing any trouble for myself or bad blood between my CTO and me, he is someone that I would like to become friends with, and learn from. Also the fact is he is a CTO of a very successful medium sized company with a lot of connections in the city where I live, so I am also very scared to get on his bad side.
The guy is a superman of course to whom I look up to, and he is only 7 years older than me yet thousands time more successful, so the concept of not enough time in a day is a foreign fact to him.
Any advise will be greatly appreciated, I simply do not know what to say.
EDIT:
Just to clarify one thing. The project itself is using a technology that I really do not enjoy, it is not my specialization nor is it relevant to my interests or anything I do at work. Additionally the problem is that no one in the company, nor anyone that I know is even remotely interested in such a technology, nor would want to be interested. I do not want to give out too many details but think COBOL but for smaller niche.