Most of us spend a lot of time thinking about how to get better--how to be happier, more productive, fitter, smarter. We spend a lot less time thinking (constructively) about how we're screwing up.

There's no mystery there. Focusing on your faults and bad habits can be pretty depressing, after all. But often, by ignoring the small lifestyle decisions that take a toll on our well-being and health, we're missing the low-hanging fruit of relatively easy-to-implement changes that will make a big difference in performance.

Just look at intelligence, for example. Science shows all the behaviors below are making you dumber. Wouldn't eliminating some of them be an easier first step towards raising your intelligence than signing up for a calculus course or committing to reading 100 books this year?

1. Poor sleep

No shock here, but it's easy to conveniently forget all the ways insufficient sleep negatively impacts cognitive performance when you're contemplating just one more late night episode of your favorite show or responding to just a couple more emails.

Here's PsyBlog to remind you: "Sleepy brains have to work harder while short-term and long-term memory is worse. Attention and planning are worse and it's easier to follow habits and difficult to create new strategies." In short, if you don't get enough sleep, you're going to be dumber. Oh, and science says you'll be less charismatic, too.

2. Too much sugar

Not only will sweet snacks cause your energy levels to peak and crash, leaving you physically drained, eating too much sugar will also impact your brain's performance. A recent study found that elevated blood sugar was linked with memory problems. The higher a person's blood sugar, the researchers found, the fewer words off a list they could remember.

3. Multitasking

Not only has it repeatedly been proven to make you less productive, but over time, doing multiple things at once also physically shrinks parts of your brain. Yes, really. The brain areas affected are linked with emotional control, decision making, empathy, and responding appropriately to rewards.

4. A high fat diet

Put down that brownie or piece of fried chicken and your brain will thank you. Recent research on mice suggests that a high fat diet causes significant damage to cognitive flexibility, a.k.a. the ability to adapt to changing situations.

5. Meetings

We've all heard the popular belief that being part of a large group can lower IQ (though the scientific backing for this claim is apparently pretty thin), but it's not just being a part of a pitchfork-wielding mob you need to worry about. "A Virginia Tech study revealed that 'group settings can diminish expressions of intelligence, especially among women,'" reports Business Insider.

That could mean meetings are making you dumb--or at least they're making you sound dumber. You probably can't single-handedly eliminate them, but make sure you don't try to use them to think up or present your cleverest ideas on the fly.

6. PowerPoint

What's another common office practice that could be lowering your IQ? PowerPoint, according to the same Business Insider article. "Commanders in the Army told the New York Times in 2010 that the Microsoft program 'stifles discussion, critical thinking, and thoughtful decision making,'" it also notes.

7. Stress

OK, this one isn't always all that easy to eliminate, but science shows chronic stress is probably making you dumber. How? Exposure to stress hormones makes it harder for the brain to encode new memories. (A short-term burst of stress, on the other hand, can briefly enhance memory.)

8. Being a know-it-all

Being too keen to demonstrate your intelligence, ironically, makes you more likely to believe, and talk, nonsense. One study showed that those who claimed to be financial wizards were actually the most likely to also claim they knew all about totally bogus, made-up financial terms. In a follow-up study, self-proclaimed geography buffs told researchers they could point out entirely fictional cities on a map.

9. Jet lag (or wacky sleep schedules)

You know you're not at your best immediately after a long flight, but research suggests that the mental deficits caused by jet lag stick around a lot longer than the fatigue and funny sleeping patterns. "Not only do we find that cognitive function is impaired during the jet lag, but we see an impact up to a month afterward," notes Lance Kriegsfeld, the psychologist behind the study.

"What this says is that, whether you are a flight attendant, medical resident, or rotating shift worker, repeated disruption of circadian rhythms is likely going to have a long-term impact on your cognitive behavior and function," he adds.

How many of these bad habits are you guilty of?