There are people who by nature, physically as well as spiritually, tend toward melancholy.
A tempestuous life-whether of holiness or of impurity-holds no attraction for them.
Contentment lies in quiet continuity.
If they have an intellectual bent and if matters of the spirit interest them, then the coziest means for self-realization is to sit and study.
The latter requires no self-sacrifice; it is the self-expression of a bookworm.
Such an individual devotes every spare moment to Torah study.
There is no contest between a Godly soul and an animal soul; this is his animal soul.
We could reasonably expect that, intellectual though he may be, he might have to struggle with his disposition in another plane, namely, sexual desire.
The capacity for sexual pleasure differs from one person to the next; and a lack of sensuality, an absence of pleasure in eating or drinking, is no indication of spiritual achievement.
Someone may not pay any attention to what he eats or what he sees.
So, too, with sexual desire.
Such an individual can sit in a study hall and be occupied with the performance of the commandments while the world around him presents no temptation.
He gets dressed every morning, has his breakfast, and goes about his business.
His single-minded focus on Torah study is not from a magnetic attraction to holiness; he is disinclined by nature to do anything else.
He could be a clerk, a professor, or a rabbi–any of these, with no change in his disposition.
Because he is a Jew, it is only right that he observes the commandments; and since he is disciplined, he does what is required of him.
His immersion within Judaism and tradition defines the directions he takes in life, and his ability to make decisions, as well, keeps him within the fold as a proper Jew.
The story is told of a scholar who traveled to the famed Rabbi Yaakov Orenstein to receive rabbinical ordination.
Rabbi Orenstein's custom was to rely on his son to examine the character of a newcomer.
On this occasion, after careful observation, his son recommended against granting ordination to their visitor.
His father, however, after speaking with the man and being impressed with his Torah knowledge, decided nonetheless to ordain him.
"If so” Rabbi Orenstein's son told his father, "do it quickly. If he is not soon a rabbi, he will become a priest!"
The son's impression was that this individual was interested in becoming a rabbi only because, being Jewish, it was his natural proclivity.
Yet it was conceivable–and could still be conceivable–that given his basic nature and potential, he could switch tracks without undue effort.
–Rabbi Adin Steinsaltz
From Learning from the Tanya, p.49+, by Rabbi Adin Steinsaltz