The Sfas Emes in parshas Beraishis writes that just as the Chayah and Yechidah parts of the soul are “enveloping lights” which surround a person, so are Torah and mitzvos “enveloping lights”, which raise a person from the soul levels of Nefesh, Ruach, Neshamah to the higher soul levels, Chayah and Yechidah. He writes further that doing mitzvos raises a person to the Chayah level of the soul, and learning Torah raises a person to the Yechidah level of the soul. Understandably, though, most people learning Torah do not reach the Yechidah level of the soul, even though they learn it with exertion and even though their main desire in life is to learn Torah. So how can a person truly reach the Yechidah level of the soul through learning Torah, as the Sfas Emes describes?
Answer:Through learning Torah with mesirus nefesh (self-sacrifice) and l’sheim l’shamayim (for the sake of Heaven).