An interesting place to examine human motivation is the world of games. People freely play games despite their being little or no extrinsic justification for doing so. No one needs special techniques or pep talks to convince themselves to play a game, they just feel like doing it.
One of the reasons games are fun to play is because they involve well-defined feedback loops of goal setting, followed by an action taken by the player, followed by a response. The player engages in an activity and gets rewarded (with points, a new weapon, or social prestige) if they complete the activity well and punished (by losing a life, needing to restart from a previous checkpoint, or by forgoing a point bonus) if they perform poorly. Similarly, people who enjoy their work are those who have feedback loops embedded within their daily affairs that give them same sense of challenges overcome and mastery gained. An example of this type of loop is the feeling a writer might experience when a sentence was typed with speed and accuracy, or that the right choice of words was used. The goal in this case is writing a good sentence. The activity is the writing of the sentence, and the reward is the sense that the sentence is good or skillful. These are feedback loops that play out within minutes or even seconds, creating a sense of great satisfaction in a short time. Our brains are responsive to short term rewards, and approaching an activity by trying to find and augment its loops can imbue that activity with a game-like quality. Loops can be about almost anything it seems. Carpenters may take pleasure from the accuracy of their measurements and cuts, whereas coders can get sastifaction from reducing their code to as few lines as possible, gettings tests to pass, or writing pithy but effective code comments.
A classic loop-inducing tool that anyone can benefit from regardless of what they are engaged in is the simple todo list. The loop structure is simple: the goal to reach is the completion of the task, the action is the work you put in to finish it, and the reward is the good feeling you get from finishing your work. Smaller tasks make the thrill of checking an item off of the list more regular and frequent so I find that they work better. At my old job, there were chunks of work called fun-size tasks that could be worked through at a pretty rapid clip. This was the most popular kind of work to be assigned to. Identify current loops in your work and tighten them up, or creating new loops is a worthwhile use of effort. If nothing comes to mind, use a todo list and try to break tasks down into fine-grained units of work.