I understand where you are coming from, Viers... However, you have already made one great step to becoming better.
Not only do you recognize what you do/have done wrong, but you've made a list of it. That's what I did and I think that's a good start.
Just get a list of a few things to work on and practice each one for about 20 mins by myself each day, or every other day. It really does help.
And this is something you have to FORCE yourself to do... it is similar to the first time you wavedashed. Even though there may be something you want to do, like wavedash grab, because you think it'll be more effective or you're more comfortable with it, FORCE yourself to run and JC grab instead. That may not be what you want to do and you may miss, but if you keep forcing yourself to do it it'll become habit.
Like I said, it's like when you wavedash the first time. 99% of Smashers when first learning wavedash can wavedash in training, but they never do it in a match... it's because it'll screw them up and they don't know how to apply it, but if they force themselves to do it they'll get better with it eventually.
I think it is universally constant in Smash that when you learn something new or try something new, you get worse, but as you continue to apply it, you get better than you were before. It just takes time.
/ramble
That probably made no sense. Point = Make a list of things and practice them.