An interesting question, however, not easily answered. I don’t think that there can be a singular answer on the surface but if we dig deeper we may find that training, whether in Martial Arts or any other sport for that matter, is fulfilling a basic need, that we have associated the fulfillment of, by training.
Learning what that basic need is, and understanding it, may give you the means by which you can motivate yourself to train when you feel yourself losing motivation and giving yourself excuses to stop.
If you can understand this process you will have a method to maintain your motivation and increase your achievement of anything that you wish to accomplish, whether in martial arts, academia or any other area of interest.
The most dominate driver of all motivation - for an organism to do anything - is that of pain or a stimulus that signals potential destruction and damage.
Some “gurus” in the self development industry have placed the focus on pain and pleasure and while this may seem to satisfy most of their followers I think that it is too simplistic. I would suggest that ultimately even pleasure can be reduced to pain as being the main driver because the seeking of pleasure is the movement away from pain, whether physical or emotional.
Therefore if we can identify that pain, which our training serves to alleviate, we have a very powerful motivation activator and driver.
Keep in mind that our emotions underlie the decisions that we make and, in fact, are integral to our decision making process. Thus we can find those things that drive us by looking at the events in our life that have evoked our most painful emotional responses, such as being bullied, homeless or other in other seemingly helpless situations. It is during these times of emotional helplessness that our drive to survive becomes its’ strongest and we may feel our motivation to achieve surge.
By anchoring to and remembering these periods we can instill a tool that will serve us at anytime in our life when we need to kick our motivation into operation, or just revive it, when it starts to fade. It is particularly powerful for martial arts and sporting achievements as the underlying reasons behind our motivation to train are often quite painful past experiences that have resulted in very emotional memories and responses.