Puppy blues or should I rehome?

For context my boyfriend and I have an 18 week old lab puppy, I did the most research you possibly could on getting a puppy (we already have a 2 year old rescue dog) I thought I was so prepared but I don’t know why I thought I could handle this, I’m in college and working part time and he works full time and luckily our puppy is so amazing, does so great in her crate, barely had any problems with potty training and regular training, she has truly been a breeze compared to other peoples horror stories i’ve heard and truly I love this dog so much but I just do not have the time or energy to put in the work, I am so intimidated by how big she will be and don’t think I will actually be able to handle her in the future snd I know that the older she gets and the closer to the teenage stage she gets the worse it will be, at the moment my classes are pretty tame because I am only doing prerequisites but by the time the teenage stage rolls around where training is the most important I’ll be in the thick on my RN program and we can’t afford for my boyfriend to work any less, I feel like a horrible irresponsible person for even thinking this because she has been so great, I don’t know what to do. Am I overthinking it is the teenage stage even that bad or messing up the training I feel that I am at such a loss and I can’t tell if I am just overthinking everything or if I really messed up.