Another advantage to knowing the rationales of mitzvos is that it enables one to become holier even in those matters that are technically permissible. For instance, with regard to the prohibition against Ribbis (charging interest on a loan), which the Torah forbade, once a person knows the rationale for the mitzvah, that the Holy One wished that Jews should do acts of kindness and to give loans with grace, he will understand that it is also proper to give a loan through a Heter Iska (a type of partnership that provides for the sharing of profits), if possible. The same idea applies in other mitzvos as well.
Another benefit of knowing the rationales of mitzvos is that it enables a person to be considered as though he fulfilled commandments that he was really incapable of keeping, such as bringing offerings. For the rationale that underlies the bringing of offerings is that the person is to internalize that whatever is being done in the offering is what he deserved to have been done to himself and this subdues his heart. And now that the person knows this rationale, he can fulfill this mitzvah even nowadays, as it is written, The sacrifices God desires are a broken spirit (Tehillim 51:19). Once a person gives some thought to the matter he can see that there are other mitzvos that he can fulfill in this manner, in spirit if not in deed.
As for those mitzvos that do not have a known rationale, one should bear in mind that “the Holy One wished to bestow merit upon Israel, and He therefore gave them an abundance of Torah and mitzvos.”
Before performing a mitzvah, how proper and fitting it is to say out loud what the mitzvah is, what is its rationale and what is the best way for it to be done. This is the straight path for a person who wishes to serve God to completely.