writing and what is good

I read over what i wrote yesterday and was annoyed about how bad my writing is ,so i have spent a lot of time trying to make it sound easier to understand , i was never as bad as this before ,  i used to be able to write things down and have confidence that i was making sense and as anyone who is writing will read over later what they have wrote and if you like what you have written ,then that is a good example about the quality and interest level
and the less rewriting you do is also a sign ,   but it seems absolutely everything i write comes out wrong and i have to go over it all  ,but worse i find i do not like what i have written and i notice that my thought process is all over the place .
An example of what i mean is if i am writing something i can start off following my thread  when some other thought pops into my head and off i go,   and on re-reading it i notice it is absolute  nonsense,it is not too bad here because i mostly am not that involved with what i am saying,  the reason i mention this because that is exactly what happens when i am out and about (allthough not recently)  my thoughts sometimes seem to have a powerfull reaction on my physical reactions  and also my mind jumps from thought to thought whatever enters my mind,  more evidence for this is the reaction of other people to my behaviour,  but" because the only people that i have been seeing are not reacting  as if i'm not doing or saying anything out of the ordinary it makes  the reaction of other people confusing .
Please forgive my writing this as it is only to try and help me make sense of what is going on and to try to put into perspective the workings of my mind.
Also i made a promise to myself that no matter what comes out when i am writing i will not erase it ,i am doing this to try and learn to write ,as a sort of practice if you like.