Why do I get so tongue-tied?

i am the EXACT same way. give me a minute to give someone advice in person, and its nothing compared to what i could do in a minute through writing. my mom got frustrated with me today cause I wasn't articulating, so she couldn't understand me. (which isn't entirely my fault, because I've had speaking problems for the longest time) but i write so much better than i talk. when i get excited, angry i start to talk real fast, and my words slur and they make so much more sense in my head. as far as what to do i'm not so sure, but what helps me is just to think through what i'm about to say, and slowly talk. it helps me to know that i'm not the only one struggling with this, and i hope it helps you too.