מרבה תורה מרבה חיים (אבות ב:ח)

Although the toil of Torah involves great effort and strain, as one exerts himself to properly understand and clarify the truth — for example, when delving deeply into a halachah in order to arrive at the correct psak — these “דאגות התורה,” the burdens and concerns of Torah, do not harm a person’s health.

When Chazal say that worry weakens the heart and anxiety shortens a person’s life, this refers to worries over parnassah and material matters, which can consume and weaken a person. But one who worries and toils over Torah is granted the opposite: Torah brings life. Such a person merits long years and receives from Heaven added חיים and peaceful days.