Its not your problem alone, Even viswanathan anand has got the same problem . I do play chess when ever i get free time during my office hours. most of my games had to given up due to in coming telephone calls. but still i love to play more and more games  with people of all ratings  simply because i loved it.   

I have the same problem and it is really irritating.  Stupid mistakes that are, or should be, obvious are just invisible to me.  I'm a good player usually, but I also spend alot of time playing while doing other things like t.v. or the phone.  Either way you gotta play less and take your time.  Maybe play longer games so you have more time and don't feel as rushed. 

i think thats all you can do i meen look at me i just lost to a 600 and well maybe thats cuz i just woke up but still if you play it too much then your just gonna over think things and thats not very good so usually when you take a break you give your mind some relaxation time which is good for it