It says in Keser Shem Tov that when a person feels some sort of simcha, they should connect with Hashem’s simcha, which is the root of all things. Also, when a person performs a mitzvah, that particular mitzvah is connected to all the other mitzvos in the Torah, since the mitzvos are directly connected to the Achdus Hashem, Oneness of Hashem. This concept is further elaborated in the Tanya, where the Baal HaTanya explains that the Torah and mitzvos are one with Hashem due to them being absolutely connected to His Ratzon (Will). The way to accomplish this is through performing the mitzvah with simcha and d’veikus (cleaving-ness).
There are times that a Yid cannot fulfill a mitzvah, and for an ehrliche Yid (sincere Jew) this can be very painful. Whether or not it be due to a circumstance beyond any person’s control, it can cause great pain to the neshomo. Rebbe Nachman says in Likutei Moharan that those times when a Yid cannot fulfill a mitzvah but deeply wants to, it is considered like they fulfilled that mitzvah. This concept is brought in the Gemoro in Maseches Brochos in regards to Krias Shma and a man who has the obligation to immerse in a mikvah before prayer, where it says if it is impossible for him to get out and dress or muck up the water to cover his lower extremities, it states there that if he has the strong desire to say Krias Shma and concentrates on it at that time, it is considered that he fulfilled that mitzvah. From this mesorah in Chassidus we can see that if a Yid has kavono in doing a mitzvah, and does it with the intent to cleave with Hashem, then it is like he did all the other mitzvos in the Torah; including those it is not possible to fulfill either due to personal or collective circumstance, such as bringing korbanos in Yerushalayim. There is a special l’shem yichud to say before putting on tallis and tefillin in the morning brought in most Nusach Sefard siddurim that states through doing these mitzvos it should be considered like we fulfill all the 613 mitzvos. We could say from this Torah of the Baal Shem Tov that we need to focus on this idea with every mitzvah we do, and if we do this, then it could be like we fulfill the entire Torah every mitzvah we do, every minute of the day.