Mistake: Talking while working out
Some workouts use how difficult it is to talk as a way of measuring exertion, and although that's all well and good it's really not a good idea to keep talking the entire time you're exercising -- save that energy for burning calories!

Mistake: Staying in your comfort zone
The majority of exercisers don't work out hard enough, and in order to make sure you're not under-doing it try wearing a heart rate monitor during cardio -- and for strength training make sure that by the time you're done you can't do another set with good form.

Mistake: Getting stuck in a rut
Has your exercise routine gone stale? It only takes your body around 8-12 weeks to make the most of a new workout, so if you're still doing the same exact thing you were doing 6 months or a year ago, it's time to switch things up.

Mistake: Training only some of your muscles
People sometimes tend to work only with the muscles that are easily visible (like anything on the front of the body) and inadvertently neglect the ones that are less visible but just as important -- like core muscles, pelvic floor muscles, and postural muscles.

Mistake: Having no purpose
How are you supposed to get any results if you don't know what you're aiming for?

Mistake: Slouching
By slouching (even just a little) during exercise you're doing two things: putting your back at risk in a vulnerable position and strengthening it in that position. Neither are good.

Mistake: Breathing improperly
Your muscles need oxygen to function, and when you stress them with exercise they need it even more. But many people don't know how to breathe properly: inhale through your nose, fill your chest first and then your belly, and then exhale through your mouth.

Mistake: Not knowing when to stop
If it hurts then pay attention if it's from muscle fatigue or if it's something else. Adjust your posture, check your positioning, and maybe try a new exercise altogether.

Mistake: Building up too quickly
It takes time for your body to adjust to new demands, so make sure your workout plan allows for gradual advances in intensity. Muscles need time to grow, but the connective tissue in the joints needs even more. So take it slow enough or risk serious injury.

Mistake: Making exercise too much like work
Working out should be fun and relaxing, not stressful or complicated.