Honesty is the best policy.
Just make sure that it is the other person’s policy too.
The best way to a girl’s heart is through her stomach.
Make her laugh till she can’t breath anymore and her stomach’s filled with air.
Always insert a form of endearment.
Make it simple, yet memorable for its impact will last ‘til the very end of the letter.

Dr. Gregory House
Time travel may in fact be possible, but it wouldn’t work like in Back to the Future. (For one thing, you don’t have worry about your parents failing to create you—you already exist.)