Most of the halachos of Choshen Mishpat have to do with one person's responsibilities viz-a-viz another person's rights. However, there is at least one halacha of which I am aware where Chazal told me what to do with my money for my own sake.
אמר ר' יוחנן דבר תורה מעות קונות ומפני מה אמרו משיכה קונה גזירה שמא יאמר לו נשרפו חטיך בעלייה סוף סוף מאן דשדא דליקה בעי שלומי אלא גזירה שמא תפול דליקה באונס אי מוקמת להו ברשותיה מסר נפשיה טרח ומציל ואי לא לא מסר נפשיה טרח ומציל
That is: On a Torah level, money creates a transaction. However, the Sages established that the transaction does not happen until the point when the purchaser takes possession, lest there be a fire in the room where the seller has the merchandise, and the seller won't bother to save the merchandise that the purchaser now owns .
The person cannot say, "it's my money and I am willing to take the risk" in order to become the owner through paying for it. (See Shach C.M. 198:9-10)
Are there any other examples where Chazal made decrees for a person's own benefit, and can this be extrapolated to a generalization (i.e. that we should not assist someone, or perhaps even hinder someone, in doing something that we deem to be financially self-destructive)?
