From 0-10 minutes after you "submit" a post, you can edit your post without consequence by clicking the [Edit] button.
From 10-20 minutes you can still edit your post but an "Edited By" message appears, noting your action. You can add a reason for the edit if you'd like.
After 20 minutes have elapsed, you can correct your earlier statement with a new post. For example, quote yourself and then add "I meant to say the following..."
If something you wrote is truly egregious or falls outside the parameters above, it is best to report your post via the Report Post feature (click the

icon for the problematic post)

and a Mod will take of it.
As in real life, please self-edit for tone and content before you hit the [Submit] button.

.