Q. You wrote that "Chassidus teaches us that a Jew has to look at the past and future as out of their hands, and to see what you did in the past as what G-d wanted to happen" and that "your sins of the past were G-d's will". I would appreciate if you could elaborate that. What is the source? Something seems wrong. Let me sin again today and tomorrow I'll say that what I did yesterday was G-d's will.
A. This is a very good question and it is one of the deepest mysteries of the universe. I will try to answer it with explanations from Chassidus and the Ramcha"l but I hope you understand the terminology (if not, feel free to ask for clarification):
Regarding one who says: I will sin and then repent, the Torah says that he will not be given the chance to repent. As for "the sins of your past were G-d's will": That is called "hashgacha peratit" [or hanhagat hayichud in the Ramcha"l's terminology] which means that everything that happens is supposed to happen exactly like that and no different, even people's sins. This does not take away our free will even though Hashem knows exactly what we will do before we did it, as the Ramba"m says, that the human mind can't understand this contradiction. Also chaza"l say : "everything is foretold, but free will is given". This can work because "ein zeman beruchaniyut" - there is no time in the spiritual worlds. Indeed, as soon as our world was created, in the upper worlds there was already "gmar hatikun" - which means that everything was already finished and perfect (as it will indeed be in our world after 6,000 years).
But then there is also "hanhagat sechar ve'onesh" [or "hanhagat hamishpat" in the Ramchal's terminology] which follows the principle of tit-for-tat [din], i.e. you sin, you pay... just like in nature: eat poison and you die, touch fire and get burned. However, to preserve our free will, the punishment is not met immediately and that is "midat harachamim" - the attribute of mercy that "sweetens" the din (judgment). That is also called "TIME". Indeed, both hanhagot (attributes or behaviors, i.e.din and rachamim - judgment and mercy) function simultaneously in different dimensions, and yet, both are true.
Chaza"l teach us that regarding the past, we should acknowledge that it had to be like that [hashgacha peratit, everything is foretold and had to be like that]. Yet regarding the present: Free will is given, and it is in our hands to choose good or evil, i.e. hanagat sechar ve'onesh. As for the future, it simply does not exist for the servant of Hashem who is supposed to live in the immediate present alone [in terms of divine service and spirituality of course, not in terms of the physical world]. We only have the immediate present and should only deal with it, not with the past or the future. That, Chaza"l tell us, is not only the truth, but the only way to succeed in one's divine service.