how do i get a way to understand this sentence
you have to understand, a day does not go by when thatdoes not weigh heavily on my conscience

Question

Answer

It means "You must understand that I feel very guilty about this every day."

Or in Chinese, 請你一定要瞭解，這件事沒有一天不讓我內疚（讓我良心「沉重」）。

Answer

you have to understand = (please understand)
a day does not go by when = (everyday)
that = (any thought, memory, past experience)
does not weigh heavily = every day I think about that thing that ...
on my conscience = (right and wrong) this speaker feels guilty about something.