One important thing to remember about avodas Hashem is that we need to be happy while involved with it. Ideally, our every action should be devoted to this, however on the whole this is difficult for most people. At times, it can even be difficult just to serve Hashem in the first place.
For Parshas Shlach, in the first shtikl, the Kedushas Levi talks about what a high madreigah (spiritual level) Klal Yisroel on the whole was in the Midbar (desert). The Meraglim (spies) were sent and they didn’t see Eretz Yisroel with physical eyes, chas v’sholom, rather they saw with their spiritual eyes. According to a later section of Kedushas Levi in this parsha, he brings from a Midrash that one of the former denizens of Eretz Yisroel said to the Meraglim that if Klal Yisroel came and took the land, it would be thievery because Hashem gave them the land already. However as we know from B’reishis, according to Rashi’s p’shat, Hashem already granted Eretz Yisroel to the Jews from the beginning of time, hence there is no thievery involved. This is how the Meraglim sinned, they had doubt brought into them by people who seemed to be as religious as they were, this we learn through a דרש brought on the word נמלים.
The Kedushas Levi says there that there are times that it is easy for a person to serve Hashem with simcha, and times it is much harder. The times it is easier are the times when Hashem Himself is happy, so to speak, such as Shabbos and Yomim Tovim. At such times there is no difficulty to serve Hashem; whereas the rest of the time it is is difficult, and a person has to arouse themselves to serve Hashem, especially to be happy at those times. Especially in a time when we can see lots of problems within ourselves and the world around us, like R’ Nachman says these problems allude to problems in the Shechinah, which means obviously that Hashem is not in such a state of happiness.
The Kedushas Levi further states that the way a person should ideally be is in the place of separation from the body, and listening entirely to the voice of Hashem, like the Dor HaMidbar (Desert Generation). This can be difficult to understand, especially as it could possibly be relevant to such simple people as us. Rebbe Nachman has a very interesting concept in Torah 91 about Emunah (Faith). The sort of Emunah we must attain is that which extends even to the hands, as he says there, meaning that our every feeling and action must be filled with Emunah. In the language of the Zohar HaKodosh, the Shechinah is directly associated with Emunah. So when we serve Hashem from a perspective of pure Emunah, we connect to the Shechinah HaKedosha, which leads us towards proper actions as Hashem desires, as separation from the body leads to being able to hear the voice of Hashem, basically the level of Ruach HaKodesh. The Arizal speaks of deciphering Hashem’s messages from day to day from birds and all natural phenomena in Shaar Ruach HaKodesh. It also says in the gemoro in Shabbos that there is no dwelling of the Shechinah without simcha. There is also a statement that there is no simcha other than Torah. We know from the Tanya that when a person learns Torah he is connected to Hashem Himself, therefore he should be filled with strong feelings of simcha.
What we can learn and apply practically from all of this is that the key to serving Hashem with joy is to serve Him with complete Emunah, the sort that spreads through the whole body. Once we reach this, which only takes a little work through hisbodedus (isolated personal prayer and meditation) and learning Torah, then we should become filled with simcha. To facilitate simcha in order to have a dwelling of the Shechinah among us, we should engage with the permitted delights of this world for the sake of unifying the Shechinah with HaKodosh Boruch Hu, as the tefillah says לשם יחוד קודשא בריך הוא ושכינתיה. Once the seeds of simcha are planted through this, then we should continue serving Hashem through this simcha and apply it to the entirety of our lives so all of our actions will be filled with Divinity and hence be considered avodas Hashem. This is essentially the path of the Baal Shem Tov and chassidus on the whole. We should all merit to delight in the world in such a way as it performs the Yichudim and Tikkunim (Unifications and Reparations) as they need to be done, through this all problems should be fixed, and we should see the Geulah Shleima swiftly within our days.