Big topic.. but I use curiosity as a major motivator and hook on my love of learning in general. I seem to get a real chemical buzz from each 'ah ha' moment so look at things in a way that might stimulate it.

I ask myself what I can find interesting, relevant to me, new to me in a task..

Although this works well over time, it can be slow as it results in lots of interesting tangents which all consume time. Stuff gets done eventually but its just not a one-by-one approach. I end up working on many things at once and switching between them which makes the whole thing more fun. I switch depending on what mood closely resembles the task. Sometimes I am in a more 'technical' mood, sometimes more 'pychological' mood, sometimes more 'musical' mood etc, sometimes more 'physical' mood. As for excercise I do dance and acrobatics because I just find gyms boring after 15 mins. Find a way that suits you rather than what 'should' suit you.

This is quite a chaotic approach that probably only works if you have the opportunity for flexibility in your schedule. I work freelance in a few different fields so can switch my time to suit me. When making promises I overestimate so as to leave me time for switching. I once heard someone say "don't do what you say, say what you do" and this had a big effect. Base your promises based on self knowledge (what you really would do) rather than wishful thinking and stressing trying to then stick to your word.

This probably doesn't work in a rigid environment where someone else is defining what needs to be done when.