I think it applies to Mike and Jesse equally and is certainly more chilling when it's about the latter. With regards to it applying to Jesse, Walter could be insinuating that Jesse does not deserve to make the decision to tell his secrets to anybody, that he avoided "flying too close to the sun" by breaking up with Andrea as Walter had tried to manipulate him into doing so. It, more or less, was the polar opposite of what Walter had said while in the soon to be fumugated house, that it was Jesse's choice and that he earned it. The implication of course is that Jesse had taken liberties by becoming involved with somebody else, especially when Walter doesn't want Brock around Jesse. As for how it relates to Mike, well, that much is pretty obvious. I liked how ambiguous it was as it relates to both of the main characters pretty equally.