I have always been perplexed by the loathing so many people have for the prayer we regularly say between the Amidah and Ashrei, commonly known as Tachanun. All one need say is the word "Tachanun" and the most common response will be, "Do we get to skip it today?" I remember frequently seeing grown men act as if they had just won the lottery, when by surprise a guest chatan walked into shul, thereby canceling the requirement to say Tachanun. I wonder how G-d reacts to the high-fives we give each other when given such an opportunity to pray less.
On one level, this phenomenon shows our true feelings towards prayer in general. Since we rarely feel that our prayers are meaningful, it appears that we view them as a burden on our time. As such, we are happy to dispense with whatever part of the prayers we can.
But there is another issue that may explain why Tachanun begets our scorn more than any other prayer. The problem with Tachanun is that it is very negative. In it, we focus on our shortcomings and supplicate G-d to forgive us. In a world more and more dominated by a very upbeat American culture, we are not so comfortable with such negativity.
While part of what makes America great is the can-do positive attitude of its citizens, to some extent, it is also what makes America shallow. Dale Carneige, a very insightful representative of American values, called one of his books, "How to Stop Worrying and Start Living". Granted, it is counterproductive to worry too much and become neurotic still a Jew is supposed to worry.
We see that the greatest Jews worried. And the greater they were, the more they worried. When R. Yochanan ben Zakai was about to die, he was worried -- he told his students that he didn't know how he would be judged by the celestial court (Berachot 28b). R. Yochanan ben Zakai! He may well have leaned this from our forefather Yakov -- when it came time to confront Esav, he too worried that he was no longer worthy of G-d's protection (ibid. 4a).
What Yakov and R. Yochanan ben Zakai understood better than us is the need for constant introspection. I am not sure if you cant fool all of the people all of the time, but I am sure that you can never really fool yourself. Besides G-d, we are the only ones who really know the true motivation for what we do. We are also the only ones who really know if we could do more. As such, we are in a position to be our most effective critics. This, only if we take the time to worry a little. Tachanun allows us those daily minutes of introspection and self-criticism that can allow us to be the spiritual leaders that G-d expects us, as Jews, to be.
Woody Allen and others may joke about Jewish guilt, but it is this very proclivity to self-critique that has allowed us to provide the Western world with its spiritual legacy. More than one scholar has noted the absence of self-critique in ancient literature of all peoples except the Jews. The checks and balances provided by our prophets who criticized the Jews each step of the way is what allowed us to avoid the inevitable decadence of all other vanished civilizations. These civilizations became drunk with their own success and were unwilling to reassess whether they may have gradually veered off the original course that brought them greatness, until it was too late.
The month of Nissan is the longest period of time when we do not say Tachanun. It is a period of rebirth, where we are allowed to weaken our level of introspection, in order to focus on the positive messages of Pesach and Spring. It is easier to rejoice in the positive messages of Nissan. Even so, we must also learn to appreciate the need for occasional but regular negativity during the rest of the year. David haMelekh was very careful in the order of the phrase "sur mera ve'aseh tov" (remove evil and do good). He was telling us that the way to attain the most positive scenario of doing good is to first find what is bad and remove it.