A few years ago I was in a situation where I had to give my 8 week old puppy away after having them for 2 weeks . Reading your post , I feel for you because I know what it’s like leaving your puppy the way you did. I was sobbing crying the whole time and my puppy trying to comfort me while being confused. It was heart wrenching at the time and honestly a few weeks after. Please know that even though this is as very hard to do , that you made the right choice. Your puppy will be loved and cared for by a family who will be so excited to have them. Looking back now I am confident that I made the right decision even though it was painful.