I accepted a research-based graduate offer from McMaster University. I applied to other schools but I did not hear back. I assumed I did not get in. So I accepted the offer I had. I know learned that I got into my dream program. However, I feel terrible to withdraw from the offer from McMaster because I genuinely like my supervisor and his students with whom I spoke. It has only been one month since I accepted the offer. I did not accept any money yet or volunteered in the lab. What should I do? And if I were to withdraw my offer, how do I go about it.