You know what it feels like. You want to tell a person the truth, that you really have a problem with that thing they do, but you can see it in your head, that they'll be mad, and stop liking you or, worse yet, they will be sad, and you'll be responsible. It's different when you badmouth them behind their backs, there's the remote possibility they might find out, but you won't be there to face the music. You'd rather have another person resent you from a distance for days, than to have to clear the air and risk having to see their reaction.
So, don't ever tell yourself you're not being honest for another's sake. It's always so that you can have the illusion of control - and because you can't know how people will react to uncomfortable truths, you prefer to avoid confrontation for ever, instead of giving them the opportunity to have their negative feelings in your presence.
Do it sometime, dare to speak the truth and see the anger in another's eyes, knowing you caused it. You can survive this, and you will.