Beginning with the Aseret HaDibrot, we often tend to classify mitzvoth as being either between man and G-d or between man and man. While the interpersonal mitzvoth are also an expression of the Divine will, the distinction is a most relevant one, reflected in our attitude towards these separate (but overlapping) spheres.
The concept of kavanah, proper intent for a mitzvah, is seemingly much more relevant in the mitzvoth between man and G-d; at times the lack of kavanah renders the mitzvah act null and void. Developing a relationship with G-d is dependent on achieving the right frame of mind and focusing on the mitzvah at hand, and hence is generally accompanied by a bracha expressing our acknowledgement of G-d as master of the universe.
When it comes to mitzvoth bein adam lechavero, intent is seemingly much less important. The primary goal here is to help the person in need and to ensure they are treated properly. It would be grossly inappropriate to waste time focusing on an unrelated, upcoming mitzvah while the hungry wait for food. It is for this reason that brachot are inappropriate when the opportunity presents itself to help others.
Similarly, the concept of lishma, proper motivation, is much more crucial in mitzvoth between man and G-d. Performing these mitzvoth to gain social acceptance is a violation of yuhara , religious arrogance, and negates much of the value of the mitzvah. After all, one is not really serving G-d in this case, but oneself. Mitzvoth between man and G-d should, when possible, personify tzniut , privacy. Only when the mitzvah is performed without human knowledge can one be certain that it is done because of G-d's command.
However, the opposite seems to be the case in mitzvoth between man and man. Here, as the goal is directed toward another person, your motivation is of secondary importance. Thus, in the final analysis, Jewish law recommends that mitzvoth in this realm be publicized, serving as they will as motivation for others. This is true even if such emulation is done for less-than-noble motives. This is the halachic justification for the many dinners that adorn the philanthropic community despite concerns about indirect lashon hara , excessive flattery, and truth-stretching. Yet if millions can be raised to help others, and we can show gratitude to those who benefit the community, we must take those "religious risks".
Notwithstanding the above, mitzvoth bein adam lechavero are the vehicle for personal religious growth. Developing our relationship to G-d is the result of years of work, honing our character as we interact with our fellow man. The Rambam at the end of Hilchot Teshuva (a most appropriate area of study as Elul arrives) states that one of the goals of marriage is to develop our love toward G-d. Only an intense, 24/7, intimate, loving relationship with another can give us the necessary tools to develop our love towards an abstract G-d.
"One is obligated to be meticulous in the mitzvah of tzedakah, more so than any other positive mitzvah" (Rambam, Matanot Aniyim 10:1). The Torah, in presenting this fundamental mitzvah, focuses on the giver, not the recipient. The Torah thus begins by warning us not to "harden our hearts nor shut thy hands" (15:7), moving to the positive "open wide thy hand". The Torah emphasizes that "the needy will never cease out of the world" (15:11). The total eradication of poverty is beyond human capabilities, and apparently is not even fully desirable. To do so would rob man of the opportunity to financially help others.
The Sefer Hachinuch emphasizes over and over again that mitzvoth are to help develop within us the traits of kindness, compassion, and empathy. In the performance of mitzvoth, others will benefit; but the obligation begins with the need to develop our character. The constant refrain of the Torah to help the widow, orphan, and stranger, because we were strangers in the land of Egypt , is directed not so much to the needs of the underprivileged but to those capable of helping. Man is naturally selfish, and tends to view world events through the prism of how they might impact on his or her life. The beauty of helping others is that it makes us feel good, thereby strengthening the bond between us. May we merit these good feelings on a regular basis.