Not only do we fail to live up to the ideals we have, we fail to have the ideals we ought to have. There are two problems here, the first pertaining more to the will, the second more to the intellect, or rather to the faculty of moral discernment. Let us consider the second problem.
It is not enough to have ideals, one must have the right ideals. This is why being idealistic, contrary to common opinion, is not always good. Idealism ran high among the members of the Sturmabteilung (SA) and the Schuetzstaffel (SS). The same is true of countless millions who became Communists in the 20th century: they sacrificed their 'bourgeois' careers and selfish interests to serve the Party. (See Whittaker Chambers, Witness, required reading for anyone who would understand Communism.) But it would have been better had the members of these organizations been cynics and slackers. It is arguably better to have no ideals than to have the wrong ones. Nazism and Communism brought unprecedented amounts of evil into the world on the backs of idealistic motives and good intentions. Connected with this is the point that wanting to do good is not good enough: one must know what the good is and what one morally may and may not do to attain it.