Mostly Useful

 My layman's understanding of muscle memory is that once your muscles learn certain activities, you can do things like walk, ride a bike, and shoot hoops, naturally, reflexively, as if on auto-pilot. I also use that as an excuse  when I get people's names wrong- "Julie, my tongue muscles are to blame for calling you 'Julia'. Really, I know your name." I think something similar applies to memory. When I consciously decide how to spell words I often misspell them, whereas if I just write and don't reflect, I'll usually spell correctly. Case in point: I had to clarify the difference between "effect" and "affect" some students and suddenly I realized I wasn't entirely certain. In short, "effect" is a noun referring to things like consequences or results and affect is the activity of  influencing. If this seems like a no-brainer to you, then you're right. I would leave a Return of The Living Dead zombie hungry with my ignorance on some days. For a more comprehensive (and interesting treatment of this, look hither:http://grammar.quickanddirtytips.com/affect-versus-effect.aspx

 Unrelated, and equally as irrelevant,  adverb and adjective confusion can produce some interesting sentences. I explain the difference between adjectives and adverbs so much during the week that I absolutely refuse to do so now. Look them up if you don't know! That's an order! What I will say is that adverbs quite often end with the suffix "ly." He ate hungrily, she walked slowly, Buster snored loudly, etc. This confuses some people learning English because although many adverbs end with an "ly," not all do. An Arabic friend once related that she was uncertain why an acquaintance of hers felt miffed after she called to tell him that he was "mostly welcome to come to my birthday party."