Being a senior in high school, I often get this look of shock - everyone knows about it, but most people don't know how it really works. I explained to a guy at work last night, and he said, "Well, I would love to have been homeschooled, but I'm just not motivated enough."
The flaw in that reasoning should be evident: motivation is not inherent - it is externally influenced.
That doesn't mean that everything around you decides your "motivational status" - but it certainly influences it.
But motivation is not intrinsically externally influenced. The intrinsicness, or as a priest friend would say, the whatness of motivation is attitude. Attitudes are decisions. Decide to do your job. It's that easy.
This motivation, the decision to do your job, should be carried out everywhere in our lives. Our spiritual lives are the most important.
Just because I wake up and don't "feel" like making my morning mental prayer does NOT mean I am not motivated. It means I am influenced to be unmotivated, or let's be honest, lazy (and in this case slothful), but I am not unmotivated.
The point that I decide, "You know, I don't feel like praying so I won't" is when I become demotivated. It's sort of like the idea of aridity - just because I am experiencing aridity in prayer does not mean I am not praying.
Which brings me to my point:
Always make your daily meditation - and the days you don't feel like doing it are the days you absolutely have to!
St. Francis de Sales would always make an hour of prayer every day, except for when he was pretty busy. On those days, he always spent at least two hours in prayer.It's kind of like a gas tank, if you'll excuse the crudeness of the metaphor. On the days you drive 100 miles you'll need eight gallons of gas, but on the days you drive 200 you'll need sixteen.
If you're "feeling" demotivated, don't be discouraged! You are not demotivated until the moment you decide to be demotivated. It's as simple as that.