It is always in everyone's power to satisfy the categorical
command of morality; whereas it is seldom possible, and by no means so
to everyone, to satisfy the empirically conditioned precept of
happiness, even with regard to a single purpose. The reason is that in
the former case there is question only of the maxim, which must be
genuine and pure; but in the latter case there is question also of
one's capacity and physical power to realize a desired object. A
command that everyone should try to make himself happy would be
foolish, for one never commands anyone to do what he of himself
infallibly wishes to do. We must only command the means, or rather
supply them, since he cannot do everything that he wishes. But to
command morality under the name of duty is quite rational; for, in the
first place, not everyone is willing to obey its precepts if they
oppose his inclinations; and as to the means of obeying this law,
these need not in this case be taught, for in this respect whatever he
wishes to do be can do.

He who has lost at play may be vexed at himself and his folly, but
if he is conscious of having cheated at play (although he has gained
thereby), he must despise himself as soon as he compares himself
with the moral law. This must, therefore, be something different
from the principle of private happiness. For a man must have a
different criterion when he is compelled to say to himself: "I am a
worthless fellow, though I have filled my purse"; and when he approves
himself, and says: "I am a prudent man, for I have enriched my
treasure."

{BOOK_1|CHAPTER_1 ^paragraph 100}

Finally, there is something further in the idea of our practical