Find a higher reason to reach your goal than just the goal itself
I need to be mentally sharp, physically and emotionally alert, and spiritually on top of things in order to do a good job for my clients. Knowing that none of these are possible without good physical fitness, when I feel like skipping or cutting a workout short, I repeat my mantra "Strong body, strong mind, strong spirit," and picture all of the people counting on me to help them. This is a far more effective motivator than simply visualizing a fit body (which doesn't cut it for me after about 15 minutes on the rowing machine!) and reminds me of the higher purposes for getting fit.
Figure out for yourself how you can expand your perspective on reaching your goal - what things will it bring into your life besides the obvious, immediate benefits? Who else will benefit and how might that inspire you to greater effort? For example, a goal of getting up an hour earlier to have time for meditation might be hard to maintain on its own merits if you're not a morning person. But if you focus on how the calmer mindset and less rushed schedule will make you a better parent, spouse or employee, you may find that the higher benefits outweigh your immediate resistance.