If your sadness is due on me,I apologize.
If you fell sad because of my fault,I would say I'm sorry.
If the one who'd broke your heart is me,I must say that I fell terribly sorry.
For the sadness I've brought to you,I fell extremely regretful.
……several versions,dear.如果是意译的话……
反正只要不是考试要求就不严格,夸张一点也没啥……
但是您咋了?非得用英文说这个?
……算了我多嘴,当俺没问,飘远……