Rav Moshe Leib Sassov says that if a person wants to make sure his day is one filled with Avodas Hashem and avoid aveiros, he should try to make sure his first deed is a good one. Since Mitzva Goreres Mitzva, once you have the first mitzva under your belt, the law of this mishna says that it should continue, as you are already propelled in the right direction. This is Mirumaz in the pasuk (Bo 13:2), "Kadesh Li Kol Bichor", the first action should be designated for Hashem.
However a person may still worry that his first mitzva may not be done wholeheartedly and therefore this plan will not help. Therefore he says, have rachmanus on another Jew. Even if your intention is not pure, the mitzva will still stand tall as you have helped another Jew regardless. This is Mirumaz in the next words, "Peter Kol" to patur yourself from all worries, "Rechem" have rachmanus on a Jew.
Even with this a person may be concerned that the Jew he helped, is not worthy and therefore his mercy was misplaced and not considered a Mitzva. To this says Rav Moshe Leib, we only need to continue the next words of the Pasuk, "BaAdam U'Babiheima" whether he was a worthy man or an animal and not worthy of kindness, "Li", Hashem says, leave that to Me. You will get your S'char either way.