People are flaming you and I see why but I don’t want to hop on that bandwagon. Honestly I really appreciate your honestly and introspection on this topic. Even though I personally have only quite a mild stutter (but like everyone I have my bad days) and have noticed a general consensus similar to yours. In my conversations with anyone in my external circle (“friends” but not very close) most people seem frustrated before I even open my mouth to speak with them. I feel lucky to have a few really good friends that are honest about it and don’t care, and I have a few who deny they even notice it, which I also hate but that’s another story. It sounds like for this person in particular, you are their closest friend, and I can understand both perspectives. Of course you are not obliged to maintain this friendship if you find it mentally exhausting or more importantly if you view yourself as somehow superior to your stuttering friend you should cut that out immediately. I would challenge you to question whether the few seconds extra it may take for them to say whatever it is they want to say is really hindering your “study” or if you’re just getting impatient with them. I wish the best for your friend and hope the two of you do in fact stay friends as I know you wouldn’t be here if you didn’t actually care for them.