Well, there are a variety of ways to combat that. The most effective solution to mental illness of any kind will involve therapy and medication working in tandem.
Caffeine is, I believe, underestimated in its ability to improve cognition. I also use nicotine but its not for everyone. While using tobacco is highly addictive, though, nicotine by itself is much less so.
I'm currently looking into supplements partly for that very thing you're talking about.
Do you take any medications? Did your doctor diagnose you as having ADD?
One thing you might want to do is work and "play" in separate places. Or, make sure that you have one task to do, not two or more, at the same time. I oftentimes find myself trying to fill out important paperwork and on facebook at the same time, so I'm trying to set aside time for fun, but grant all of my attention to doing important tasks first (when the caffeine is especially active) in the morning.
If you could elaborate on your condition that will probably increase the quality of responses.
If you have legitimate ADD, and don't present as having a psychotic disorder or substance abuse problems, a doctor shouldn't have a problem working with you regarding medication. But the therapy is key. I think too many people forget that.