2. Saying they "get it" when they don't. This is a huge annoyance that I struggled with when I was a teacher. Smart people will listen and then tell you "hmm I don't get that, how does this follow from this?". Retarded people are really eager to show how smart they are so they want to say "ok, I get it" as quickly as possible, but they'll say it in a really uncertain way that's obvious they don't get it. And then if you ask what part they don't get, they'll say "all of it".
3. Believing they are "too dumb" to do something. Maybe they are dumb, but that's almost never actually the problem. It's almost always laziness. Being dumb doesn't make most things impossible, it just makes them harder. This usually comes after you try to explain something for a while and then they get frustrated and give up and say "ugh, I'm just too dumb for this" (which is also an annoying plea to be told "no you're not too dumb"). In reality they are too lazy and not willing to put in the hard mental work to do it. Smart people know that some things are hard and don't come easily and you have to work at it for a while, and if you aren't getting it, it's usually because you aren't working enough, not because you're too dumb.
4. Thinking they're doing a bad job because they're "too good" for their current position. Every McDonalds cashier thinks they could be head of corporate marketing if someone would just give them a chance. Yes, they suck as a cashier and are totally irresponsible and don't come to work on time and don't take any initiative, but that's just because they're "too good" to be a good cashier. Of course this is just fantasy and self-sabotage.
5. Believing that "the system" is somehow to blame for their lack of success. Most of the underemployed believe that there are phantom hands somehow holding them down, or that society should somehow be different in a way that would benefit them. The reality of the world will always be that a minority get the spoils, and you can either earn your way into that minority or not.
6. Believing there will actually be 7 items when the title says so.