It is really important to know what we think and how we think or u can say how we create a self defeating behaviour :: so "REBT" is the research of psychologist Dr Ellis ::
Events and circumstances do not cause your reactions. They result from what you tell yourself about the things that happen. Put simply, thoughts cause feelings and behaviours. Or, more precisely, events and circumstances serve to trigger thoughts, which then create reactions.These three processes are intertwined.You can learn the whole thing by below link.
[..I hope, it will be very effective for stammer to know this thing....]