The Baal Shem Tov was once standing at the entrance of a certain Beit Midrash where the local Jews invited him to enter. However, the holy chassidic Master refused to enter the Beit Midrash and the Jews started asking him for the reason.
"Because your Beit Midrash is full of Torah and Prayers which don’t leave me any space to enter !" responded the Baal Shem Tov.
Suddenly the Jews understood his reason. A Jew who is deeply involved in studying Torah and praying to G – d should do so with a certain level of Kavanah (concentration).
If you just learn and pray as a habit and without any deeper emotions and the intention of feeling the closeness to G – d, your prayers don’t go up to the Creator but remain down here in the lowest world of Asiyah.
In the case of this particular Beit Midrash, the local Jews were studying and praying but did so without the necessary Kavanah. Thus, their prayers didn’t rise to the upper worlds and remained in the Beit Midrash. The Baal Shem Tov felt it and, therefore, refused to enter the building.
I have heard this Baal Shem Tov story at different occasions and the narrators always claimed that it was a Reform Synagogue. However, I read the original story today (the Baal Shem Tov on Parashat Va’etchanan) where there is no mentioning of any Reform background. It also cannot really be this way, as the Reform movement came into existence much later.