Are you depressed? Are you working by yourself? I had a similar thing, took about 6 months almost completely off. It helped a bit, but I'm still not on the same level. Seems that change in environment may help.
If it's in your area of expertise, can you get a local client and work from their office (active environment) a couple of days a week? I noticed that I do a lot more shit this way. At home it's a bit different... Sitting by myself... Some days just listening to a lot of music... watching movies... reading... shit like that...
However, it helps to start the day with 20-30 min. workout and sometimes with a good book that gets you thinking about business, life, motivation, etc. My problem is that I kind of lost most of the goals... Just like you said, kind of lacking a reason... I know, it sucks. Was thinking to get some addy or something too, but don't think it's worth it. Tried it once, then ended up going out to the bars and pissing a lot of chicks off, it makes me mad or something. Drinking a lot of coffee - used to work, now it doesn't...
Setting a schedule sucks for me too - some days I do get into it and work till I am about to pass out - work while I feel like I can do a lot of shit - then, wake up at like 2pm pissed off that my schedule is all screwed up again... Oh well, I am just happy that I am at least half productive now. Was a lot worse before. Used to stress a lot about this shit, now I kind of take it as a natural thing... May be I do need to get more life and relax a bit, it's not all about work for me right now I guess.
Thinking to go fishing this weekend, etc... Had like no normal daily activities before, just some family, work and sitting around computer all day... Relax a bit. Do little tasks - I bet you can focus on those. Like 2-3 hour ones? Break everything down to the little tasks if you have to.
Hack edit: Needed to separate paragraphs