I usually try hard to put my best into my projects but there are other factors I need to contend with. As a computer programmer, I find myself constantly waiting for the muse (you know I once noted that "when you find the muse, RUN"). The inspiration you need to bring out the genius in you.
There are times too when you are battling with some health problems which sort of ends up affecting your work performance. Sometimes, it's our sleeping habits. For example I am a late sleeper and of course you know the "early to bed, early to rise lullaby"....For me it's the opposite. I have done all I could to change that, and it quite worked, except that it ends up putting me in a bad shape. I try to go to bed by 9pm but I don't get to sleep till 1am or 2am only to be woken at 6am by a screeching alarm I had set myself.
Once, I read a book called "How to sleep less and be efficient" and that even got worse when I tried applying the principles in the book. I have not still gotten answers but rather than go to bed early only to wait till 1am, I spend the time doing something worthwhile until I am really ready to sleep.
In a metropolitan city like the one I live in, traffic congestion is another time sucker, many of us who live here spend an average of 4 hours in the traffic everyday and by the time you get home or to work, you are already tired. To overcome this, I try doing a part of my work in the traffic, especially the thinking part or I simply read a book.
Finally, our biggest limitation is us. I usually tell myself that inspite of all the limits imposed on me by my environment(traffic, inspiration), my nature (sleep) and any other form of limitation there is, to break through, to break barriers and limits, I would have to first break myself.
If you really want to succeed, first break the greatest limit-yourself!