So I think about ways I get get back into those cycles quickly. To do that I try and cut up my work into the right size chunks, have a plan, and leave work with an "easy win" so I can get back into the loop again quickly.
Some examples. Hopefully I'm not descending too far into life-hacker wankery here ;-)
* I TDD code, and always try and leave myself with a failing test. If I'm interrupted and don't have a failing test I will deliberately break something or hit undo enough times to get a fail so I have an easy win when I get back.
* I don't track time on task. I do block out time for tasks - and track non-relevant interruptions during that time and see if there are ways to stop 'em happening.
* I run a personal kanban board for stuff so I can keep that continual ping of reward happening during the day.
* I breakdown tasks as they come in so they I can get little reward pings on a regular basis.
* When I have real problems getting into flow I give myself automatic rewards (do 20m on X then you can do 5m of fun on Y). Similar to http://en.wikipedia.org/wiki/Pomodoro_Technique. Once I get started the normal task-achievements often mean I don't actually end up doing Y - it's just a personal hack to get me started.
Basically - fake the reward cycle until the real one takes hold.
Make vague sense?