Its situation based mostly and also it can become habit bcoz of your repetitive behavior or mindset then you will also stutter on comfortable situations . Its deep-rooted , sub-concious mechanism of protect ourself from danger i.e an bad stutter and negative impression . Just accepted that you stutter sometime but it doesnt define you and make your identity as a good fluent speaker thats where recovery starts . Stuttering is result of your habit , thoughts , and beliefs just change that and stuttering will be almost gone . Don't judge yourself or let others judgement affects you ,and before going into speaking situation always be positive and aware of your thought and body , and in the middle of situation just ie middle of block , don't force or feel pressure just stop let that block dissolve and DON'T TRY TO SPEAK or THINK Of Speaking bcoz our brain has built shortcuts . ie speaking > danger (getting stuck , humiliation ) > Forcing and uncontrollably faster movement speaking habits > avoid , run or to overtly stutter . But over times our brain create shortcuts that speaking > () > avoid or overtly stutter .