Great! I'm glad you're seeing results. You're going to feel hesitation at first when you try it because it's not something that someone would normally do. But if you get used to moving your mouth and tongue appropriately it's going to counter your speech blocks, regardless of where someone is at mentally (whether at home drinking coffee or under high distress). For words with vowels: Remember that a vowel such as "a" will require 2 movements of the mouth. "Ay". Meaning, it's possible you're not getting to the phonation position of the "y" fast enough to make the transition. The more you practice, the better you'll get at it.