Little Mistake Spoils Everything.

Today I will send the programming task via Email, I completed the task for 3 days, from Tuesday to Thursday. Then I changed the format of the task file from CPP format to txt, then I added my student number in it, and I sent it to the specified email. I just realized that I wrote wrong email from the specified and today has passed from 3 days, I tried to contact him, I explained that I was late in collecting the assignment for writing the wrong email and he forgave me and accepted the assignment I had sent even late.
I will be more careful in writing email or other instructions, so as not to happen again. Because each lecturer has their own characteristics in teaching. Lucky me, because he forgave my mistake and I admit it. I'm so scared If I'm unforgivable and my job is not accepted and my point was bad. I have promised him the roots more cautious again, and he told the song if it happened again then my point will be bad.
And today he gave the task again, the task was more difficult than yesterday, and more complex then I should have extra time to do it. Usually I do it with my friends will be easier in solving problems, quickly finished, quickly collected, and do not forget me to be careful in writing email. I'm really scared If this incident happens again and something bad happens to me later.