If the first 2 motivational tactics don't fare well for you here are 2 more that I find extremely effective.
The first is to remove any consequence from the goal, thus taking away the fear of failure which will sometimes cause you to self sabotage. It's like you are treating your goal as a science experiment to see if you can prove or disprove your hypothesis. For example you may ask yourself 'I wonder what would happen to my physique if I ate cleanly for the next 6 weeks?' Or it may be " I wonder what would happen if I saved 10% of my paycheck for the next calendar year? Would that give me enough to travel for a month?" Again looking at your goals this way removes any negative connotations a particular goal may carry.
The next technique I have found to be very useful. You see the most common way a person may motivate themselves to reach a particular goal is to give themselves a reward both at the completion of that goal and for different milestones along the way. This is good except that many people will rationalize their failures away until they feel justified rewarding themselves whether or not they've actually achieved their goals. Secondly, if you don't want that goal bad enough or you don't want that reward bad enough it won't be a powerful enough tool to pull you through the tough times. You will likely quit and say " Oh, I didn't need or want _______ that much anyway." Thirdly, our society is so weak that many of us haven't even achieved significant goals in our lives to begin with therefore we can't relate to that feeling of absolute extasy that comes with actually reaching a worthwhile goal.
So what is your alternative you are asking. Create a negative consequence for not achieving your goal. You see all humans are motivated by 2 powerful factors; to gain pleasure and to avoid pain. Sometimes it's just one and sometimes it's both. So if pleasure isn't enough to keep you going maybe the absolute fear or disgust of a particular negative consequence will shock you into completing your goal.
A consequence might be if I don't drop 20lbs by May 20th I am going to allow my friends to post the most humiliating pictures and videos of me that they can find on the internet and publicly embarrass me. Or if I don't sell 50 cases of product by March I will eat this can of dog food. Use whatever frightens you the most. And if you are extra masochistic you may even include a punishment for each individual screw up along the way to your goal something like doing 500 Hindu squats should you have an unplanned cheat meal, or give part of your commissions cheque away if you aren't 50% to your sales goal by the middle of the month. It it especially important to tell friends and family if you are using this method so you have extra accountability.