To some people, brush their teeth in the morning is a part of life and is an all important necessity that is done automatically, to other, brushing their teeth is a chore and the only reason it is done is to avoid the conceivable outcome of a cavity that will not be pleasant at all. In that case their motivation is the simple fact that this so-called boring chore can lead to a more unpleasant outcome if it is not done now, even so the other half doesn't see it as a chore at all and as such they do not need motivation to do it.
In that same good sense, many people live by the "it could be worse" philosophy and those persons tend to not need much to be actuated. When they suffer a minor or even major set back, they tend to concoct how bad it could have really gotten and choose instead to focus on what is left and try to rebuild from that. I guess you can say that they also fall into the "glass is half full" bunch. But the simple fact is that if you linger over the worse part of the trial by ordeal, you will quickly become de-motivated and depressed and will consequently prefer to abandon than start again.
Another great saying that orders the life of most motivated people is the one that arrogates that all things happen for a reason. While you do not have to inevitably believe that, you can opt to think that if something goes wrong, it only bechanced because it is preparing the road for something to go actually right and if it had not in fact failed, you would have come down the wrong road under the impression that it was the right one until you access that road block. Can you conceive of if that were true, you would have confident yourself that you were on the right path because it looked good from the commencement, but when you meet that roadblock without any way over or around it, you will none but two choices; stay in that one spot for the rest of time, or change of mind and go back, then start over on another road.
The aforesaid ways of looking at life may not seem hardheaded, but they will help you to keep your saneness and stay focused when you have a task to complete. It may be a small task that can be completed in a couple of minutes or a few hours, or it may be a task that will take you a few months or a few years. Whatsoever the task may be and even so long, the best thing that you can do for yourself is to assert a positive mental attitude and that will keep you motivated.