It's true you often get things done early in the morning or late in the evening.
The rest of the day you get interrupted by many things (phone, icq, mail, meetings, people dropping by...)
But if you want communication amongst people, interruption is certainly an inevitable drawback.
To avoid such things I see some solutions:
- If someone drops by, evaluate if it's urgent, if not finish your current task and go find that person afterward
- When I want to concentrate to get something done, I sometimes turn off Outlook...
- Meetings should mainly be standup meetings
- Try to organize your tasks with priorities and stick to them (not always easy)