Como eu posso falar ''de um dia pro outro'' em inglês

Há diferentes maneiras de dize-lo, uma opção é: ALL OF A SUDDEN

And also "there's no magic formula to instantly change yourself/...change your ways/...your behavior/...how do you feel or react to something (name it).

There is no quick fix.

Context # 2:
There is also the 24-hour thing, in Rio, you don't take your car to some repair shops, you have to book the service first. There are no eleventh-minute calls. (ligação de última hora, tipo você viaja amanhã e precisa fazer revisão)

Some kinds of repairs, even if you don't book (an emergency, the engine seized up), in such context we can safely say your car doesn't get repaired within 24 hours. It's not the average time of repair as well.