The foundational image for spiritual growth is one of constant, incremental ascent rather than a single leap: the path of the righteous is compared to the dawning light that brightens steadily until noon in Mishlei 4:18, the one who delights in Torah is like a tree that continually yields fruit and whose foliage never fades in Tehillim 1:1-3, and Hoshea 14:6-8 describes Israel's flourishing like a blossoming lily striking deep roots and spreading boughs.
This world is cast as the corridor whose entire purpose is the performance of mitzvot that lead a person toward his ultimate destination, as Mesillat Yesharim 1:3-4 explains, citing Chazal's description of this world as a corridor before the World to Come. The Rambam similarly teaches that a person trains himself into fixed character traits only by repeated practice until the proper mean becomes second nature in Mishneh Torah, Human Dispositions 1:7, while Duties of the Heart, Third Treatise on Service of God 3:1-5 distinguishes submission to God induced by Torah study from the deeper submission that arises from an inward intellectual conviction, noting that the former leads to the latter as a step of ascent.
Active self-inspection is the engine of growth: Mesillat Yesharim 3:6 calls for constantly reviewing one's deeds to uproot bad habits before they become sin, Mesillat Yesharim 6:18-19 identifies laziness and its endless excuses as the chief obstacle even once a person already knows his duty, and Mesillat Yesharim 7:20-22 argues that outward alacrity in action actually kindles inner enthusiasm, so that acting swiftly in mitzvot intensifies the desire of the heart. Berakhot 28b frames this as cultivating a fear of Heaven equal to one's fear of being seen by another person, and Mesillat Yesharim 26:17-19 teaches that only after acquiring all the prior traits, from watchfulness through fear of sin, can a person cling to God with love and awe.
Teshuva itself is described as an ongoing, voluntary process rather than a one-time event: Mishneh Torah, Repentance 5:1-2 establishes that the choice to incline toward good or bad always remains in one's own hands, and Mishneh Torah, Repentance 7:3-4 extends the work of repentance beyond acts of wrongdoing to character traits like anger, envy, and the pursuit of honor, which are harder to uproot precisely because they are not discrete sins.
Humility and openness to instruction from any source are presented as prerequisites for growth: Pirkei Avot 4:1 defines the wise person as one who learns from every person, and Pirkei Avot 2:4 warns not to separate from the community and not to judge another until reaching his place, while Tanya, Part I; Likkutei Amarim 30:1 applies this same teaching to demand that a person weigh his own level of service honestly before every other person, however lowly.
Tanya frames ongoing growth as the perpetual struggle of the 'oved,' one actively engaged in battling the evil inclination, as distinct from the tzaddik who has already attained victory, in Tanya, Part I; Likkutei Amarim 15:2, and cautions that sadness over one's distance from the level of a tzaddik stems from conceit, since the honest work of the benoni is simply to subdue the rising thoughts of the heart, as described in Tanya, Part I; Likkutei Amarim 27:3-4.
Constancy in Torah study is itself treated as a vehicle of growth: Berakhot 17a:6-7 praises one who grows up in Torah and whose labor is in Torah, urging that one gain knowledge of God's ways with full heart and soul, Berakhot 11b:10 discusses the blessing recited before Torah study that calls for the words of Torah to be sweetened, and Eruvin 65a:11 records how the Sages disciplined themselves against distraction and excess sleep to protect their Torah study, while Mishneh Torah, Torah Study 1:13 notes that reward attaches even to study not commanded, though at a lesser measure.
Several sources emphasize that each action carries cosmic weight beyond what is visible: Nefesh HaChayim, Gate I 4:1-3 teaches that no detail of a person's deeds, speech, or thought is in vain, since each rises according to its root to effect results in the loftiest worlds, and Shem MiShmuel, Bamidbar 1:2 describes the inner spiritual battle that a person must wage with strength of heart as though the whole world's balance depends on him, drawing on the teaching to view oneself and the world as evenly balanced between merit and guilt. Shem MiShmuel, Ki Teitzei 6:8 likewise links human toil and effort to the threefold structure of body, soul, and intellect that a person must perfect.
A cluster of sources stresses that spiritual ascent is necessarily gradual and ultimately dependent on divine assistance rather than human effort alone: Michtav MeEliyahu (Rav Dessler) describes how a person must recognize spirituality as true reality and then strive to share it outward through chesed, while a second passage from the same work, Michtav MeEliyahu (Rav Dessler), teaches that ascending even one small spiritual level through one's own power alone would take centuries of unbroken effort, yet God demands only the opening of a needle's width and supplies the rest through siyata dishmaya. Likutei Moharan 48:3 roots growth in the combination of justice and chesed drawn from Micha's charge to walk humbly with God, and Likkutei Torah, Behar 1:11-12 and Likkutei Torah, Sukkot 1 use the agricultural image of planting and decomposition to describe how acts of charity and kindness, and the humbling confessions of the Days of Awe, prepare the ground for love and closeness to God. Sefat Emet, Vayikra, For Shabbat HaGadol 9:2 ties the capacity to receive sanctity to the exertion of the六weekday days of labor, and Otzrot HaRaayah, Volume 6, Part ב 71:4 and Otzrot HaRaayah, Volume 6, Part ב 77:11 call for constant, broad engagement across the disciplines of Torah, ethics, and spiritual study as the path toward the highest, most inward levels of holiness.
Other sources address the disciplines and communal structures that support this inward growth: Ein Aya, Shabbat 6:21 contrasts a people's pursuit of quantitative wealth with the choice of qualitative richness, arguing that only divine illumination enables a nation to choose depth over superficial abundance; Rav Samson Raphael Hirsch explains the symbolism of hair-growth in the nazirite's self-imposed isolation as an act of inward spiritual and moral self-education; Arukh HaShulchan, Yoreh De'ah 264:11 notes that the preparation, pure thought, and proper intention accompanying a mitzvah add greatly to its effect even though the physical act is uniform; Contemporary Halakhic Problems, Vol II, Part I, Chapter II Blessings and Rituals states that mitzvot are designed to refine character, but only when performed with reflective, introspective awareness rather than mere mechanical observance; and Rav Eliezer Melamed (Peninei Halakhah, Days of Awe 6:11) and Rav Eliezer Melamed (Peninei Halakhah, Zemanim 11:5) describe teshuva as liberating the soul from the bonds of the evil inclination and describe how dedicated Torah study sustained the spiritual center of the Jewish people through exile.
Among the poskim who address this question directly, Revavos Ephraim (Revavos Ephraim 7:381) takes up the request to increase pleasure before God by strengthening and continually increasing one's sacred service, rising level by level toward the stature of the holy forebears and striving for every form of perfection humanly attainable.