There’s debate about how a stutter comes to be. And as there’s no sound evidence that points to cause .. I imagine debate will continue. Some argue that it is a result of injury, some suggest it’s hereditary, while others believe it’s a combination of a learned or physiological disorder. Either way, there are a lot of self help strategies that can improve fluency and rewire the brain, so to speak. The one I’ve found the most useful is a smooth talking technique. Practice blending sounds into each other at a slow rate, not allowing for gaps of sound between words. Slowly increase the rate of speech. Practice meditation in tandem. This has been my most effective self therapy to date. Good luck! Know that stuttering does not define you, it is simply something that you do sometimes. And remember, adversity builds character.