You're right. I really knew it was a habit for me because I realised I wasn't as social as I was in school and the only time I engage in conversations would be in situations where I stutter. I lost touch with speaking normally and I started to stutter while talking to myself or reading in my mind as well(not actual stuttering, but my tongue would slip out of position. Basically poor control). Then all this became a habit and I found myself being amazed for not stuttering in certain situations and being amazed at it. I was so amazed that I would repeat it to myself and I would find myself stuttering. We all should strive to not stutter with ourselves so that we can expand our horizons effectively.