Depends. Hear them out first, because maybe they're seeing something you're not. All the "rah rah you can do it" cheerleading is wasted on you if you have a subpar app or a poor work ethic. Heck, if you're being totally unrealistic, they're doing you a favor by giving you a dose of hard, cold reality (although hopefully it's given kindly). But if these people don't have any good reasons for thinking you won't make it, then why do you care what they think? Talk about it to someone else instead.