How do you define regret? Do you feel sorry for those you'll leave behind? Do you think about what could've been?
In case of feeling sorry for others (parents/friends/etc)... I totally understand why it feels so hard to overcome that but it's really not about them. Nobody asked me if I wanted to come to this world. Nobody mentioned to me the dangers awaiting me. I am my own being and I don't owe anyone anything. They will be hurt, no denying that. But the world turns. A week, a month, a year, a decade, nobody knows how long it will take, but at a certain point, you won't be their biggest problem. It is life and the show must go on.
"All the world's a stage,
And all the men and women merely players;
They have their exits and their entrances,
And one man in his time plays many parts,
His acts being seven ages." (Shakespeare, As You Like It, Act II, Scene VIII)
If you think about "what could've been", I don't have much to say. Personally, I don't pay much attention to that. The possibilities are endless, but the reality is what we have.