Ooh, so many threads about this (don't worry, I won't merge right now, I'm too tired at the moment)
The truth itself hurts. It's a powerful thing.
The only thing we can control is the manner in which we tell the truth. In that, I think as long as you are thoughtful, kind, and respectful (omg, I sound like a broken record here, I've written this almost ad verbatim in 2 other threads) and temper your truth to be appropriate for the situation - it's all gravy.
There is only so much that you are personally responsible for when you tell the truth, the rest is just life. I.E. "don't shoot the messenger".
If you are telling your own personal truth about a previous transgression or how you feel about someone or a situation - a lot of times, your own discomfort should not even be an issue. You come clean because that's what you do and let the chips fall where they may.
I think all things being equal, being aware of the impact of truth on other people is a great thing (and often a gift of awareness or thoughtfulness that not everyone excercises or has), however, the impact in that moment shouldn't necessarily be the deciding factor about whether or not to tell the truth.