A good method to try and skip some of these boundaries that I got into a while ago was that of using a letter that you find very easy to say, so for example, I have trouble with d's sometimes. So e.g. 'I have to study disabilities for my final end of the year essay.' would become; 'I have to study adisabilities for my final end of the year essay.' If you do it quickly and efficiently enough people do not notice and they just take you as someone saying the correct word as mostly people just catch on to what you're saying regardless. Be careful if you do try and adopt this routine/method though as it gets rather addicting and it forces you to not break through those barriers. Do it for a while, but try and not use it for too long.