What you describe are rather typical syndromes of burnout, which is a mechanism, if you will, that our brains have developed to protect themselves. It’s quite common and definitely more common than we think.
Personally, I’m not a big fan of “Do thing X by date Y” because this kind of thinking can quickly undermine the power of daily routine and habit. If you have this vague goal or thing in the future, the satisfaction of being rewarded only comes at that point in time when the goal is reached. This, by itself, is not only an exercise in frustration, it is also extremely demotivating because our brains are really excellent at handling daily affairs, but they suck when it comes to reserving a spot for “that thing in the future.” Even if the ambition for the task is there, it’s useless if you don’t train your gray matter to tap into this resource.
That is not to say that you should not reach for the stars and set goals for yourself–quite on the contrary. However, if you do, you should first empty your mind of all the “ifs” and “buts” and then concentrate on the steps that are required to reach your goals–better still if you write them down.
To illustrate this point, let’s say your goal is to learn the 2000 or so kanji required for reading fluency in a year. There are only so many days in a year, and there will be days when life gets in the way. So, if, let’s say, you get 300 days for proper studying, you would have to learn 6 and 2/3 kanji to reach your target. If you don’t feel like rushing, you could lower this number to 5; if your retention is really good, to 10. For each new symbol, you’d have to study a) the most common kunyomi and onyomi readings, b) stroke order, and c) two to five common word combinations. Depending on your efficiency that’s probably a minimum of 5 minutes per kanji plus 30 minutes for review. At 5 kanji per day, we can round the time required up to 1 hour each day. That’s fine, we now have our requirements.
Next step is to ask yourself if you can set time aside every day for this task. We’re all on a schedule, and time is usually a hard-earned commodity because we also want to do our favorite things. However, that point is also most easily assaulted if we ponder hard enough: “Well, if I don’t watch this, play that, or do whatever, I can easily set the time aside for studying.” Even if you can’t study an hour at a time, everyone is able to do it in 15-minute brackets.
With the plan of action complete, it is of pivotal importance to put some sort of reward system in place. This can be as simple as checking an item on a list that you review daily. There are also a lot of habit apps available that work like RPGs. Or you say to yourself “Okay, I finished my studies today. Well done, me!” The reward does not have to be tangible, and whatever works best for you, works best for you. You could also buy your leisure time with studying as in: “I studied for an hour, now I can watch my favorite anime for an hour.” If you have cash to spend, you could acquire two large glass jars or similar container and 300 marbles. Put all the marbles in one jar. Write “target” or 献身 or whatever you like on the other. Each time, you finish your daily allotment of study time, put one marble in the target jar. This way, you can visualize your progress, which helps with long-term motivation.
The point is, there are myriad ways to motivate yourself daily.
But what about the days where I simply cannot or don’t feel up to it, I hear you asking. This, frankly, is where a lot of people fail simply because they fall into a nasty positive-feedback-loop trap that goes something like this: The first time you fail doing something, your brain remembers the negative impact–if you don’t actively go against the feedback loop, that is. The next time, you fail to do your studies, your brain recalls the first time, next the first and second and on and on. Every time you fail at something, you feed the loop. Best case scenario, you end up working alltogether. Worst case scenario, this “autoreinforced negativity” can have a malignant impact on your life and health.
In order to combat the feedback loop, you could acknowledge the “failure” in a positive manner: “Yes, I missed studying today, but it’s not the end of the world, and I don’t need to feel bad about it.” Or, turn it into a positive opportunity rather than a missed one: “I will make up for it tomorrow by studying two hours!” or “I can’t concentrate on this particular thing today; instead, I’ll do something different that’s in the same vein.” This way, it is much harder to become demotivated because you did not really fail.
I know you didn’t come here to read a novel, but I feel that such motivation tactics can be applied to virtually all aspects of life. And, again, most people only reward themselves once they reach the end goal without acknowledging the many tiny, but equally, if not more so, important steps in-between.