The Beinoni is someone who should see himself as a Rasha. He is not a Rasha (an evil person in the true sense of the Alter Rebbe’s description of what an evil person is). However, he is also not a Tzaddik (a righteous person). But still – he must see himself as a Rasha.
While externally, he really does function as a Tzaddik, the truth is that there are only certain times in his life that he truly functions as a Tzaddik, like when he is involved in prayer and Torah study. Then, he has these flames of a fire of love towards God and he wants nothing more than to serve God. But – when, for example, prayer is over, he returns to his ordinary state where the animalistic instinct kicks in again. Of course – let’s be clear, he does not sin in any way whatsoever. But still, thoughts of sin enter his mind – though he pushes them away immediately.
The Beinoni involved in the study of Torah connects even more with the “Tzaddik” side of himself. But this is only because he is immersed in Godliness all day long. Were he to stop his involvement in the Godly study and activities, he too would return to his ordinary state – just like the case of the Beinoni does after he prays.
This is why Rabba considered himself a Beinoni as we had learnt in the beginning of Tanya. Because he was always involved in Torah study, he could have thought of himself simply as a Beinoni involved in Torah study all day long rather than a Tzaddik. At that point in time, he would have certainly been connecting with God like a Tzaddik, but then again, even the Beinoni feels this way when he is involved in study. Hence his considering himself just on the level of the Beinoni (the average man.)
The Tzaddik, on the other hand, has so totally removed the evil inside his heart, that it remains totally void of any evil. The Beinoni continues to have the evil in his heart. It is just that at certain times, the evil falls asleep while he is engaged in Godly activities. But when those activities are over, the evil awakens yet again.
