There are no tricks for ensuring that one will not trip and fall, no matter how righteous one has been or for how long.
The Talmudic sages deal with this problem, but after lengthy analysis and numerous examples they fall back on the generalization that no one is safe from temptation.
Consequently, no one is in a position to despise backsliders.
Over the years one learns one’s own weaknesses and how to overcome or at least circumvent them.
One learns to create for oneself those inward and outward circumstances most conducive to continued progress, without fear of experimentation or others’ contempt.
One who is unfamiliar with such problems or, even more so, one who has never built up for himself a way of life that can serve as a bulwark against them is much more likely to stumble.
–Rabbi Adin Steinsaltz
From “Lapses and Crises” in Teshuvah by Rabbi Adin Steinsaltz.