“Can I be honest?” should be followed by something kind, not just something true.

That opening has turned into a licence, a way of announcing that what follows is excused from the usual rules because it happens to be accurate. Accuracy was never the only requirement, though, and plenty of true things get said mainly for the relief of saying them. Honesty aimed at helping and honesty aimed at unloading feel identical from the inside. The giveaway is whether you thought about how it would land.

Before you use that opener, work out what you want to happen next. If the answer is only that they should know, wait. If you can name what would actually help, lead with that part.