Giving people credit and a sense of accomplishment can go a long way. One way to motivate people along these lines is by showing a bit of upfront progress. We can reward people sooner as they start a task rather than wait till later. This way the perception of reaching the end becomes more attainable. The Goal Gradient Effect (Kivetz, Urminsky & Zheng, 2006) suggests that humans will complete a goal faster the closer they are to the end. Practical applications include: pre-stamped cards, rewarding for signing up, and savings accounts with non zero sum balances at the day of opening.
Try Upfront Progress
Good Optimizations: Gradient Variations
We can measure the effect of something in a scientific way by varying
the strength of the possible cause across the variations. Scientists do
this all the time with their white lab coats on. Let's say someone is
testing the effects of gifting on sales. In this case, they might setup
their test with the control having no gift, with B variation receiving a
gift of low strength, and then further adding a few more additional
variations with better and better gifts. If gifting does end up showing
an effect, then the test result should suggest some degree of
correlation. So that's just another idea for you to setup an experiment.