I took on a hachlatah, but now I wish I hadn’t. May I stop it?
If one undertook a minhag tov (positive practice) such as prishus (abstaining from a certain indulgence) or a chumra (an added stringency in the performance of a mitzvah) with the intention of adhering to it permanently, or if they did it three times—after which it becomes halachically binding—they would have to do hataras nedarim (have the vow nullified by a beis din) if they wish to stop doing it. This is because the new practice has acquired the properties of a vow.
However, if the practice was based on a mistaken assumption—such as the incorrect notion that one should stand during a certain part of the davening—then it’s deemed a minhag ta’us (a mistaken practice), and it may be discontinued without resorting to hataras nedarim.