Weak or sore knees are another sign that your form has room for improvement, says Zoeller.

"Your knees could be internally or externally rotating during squats. If you continually rotate in or out during any sort of squat exercise, you are adding added stress to your knee joint," she explains. "Look in a mirror and take an unweighted squat at a slow pace [and observe if] your knees roll in towards your big toes (internal rotation), or out towards your little toes (external rotation). If you begin to notice internal or external rotation, practice doing unweighted squats slowly until you are able to squat straight down without internal or external rotation."

Again, it's all a matter of pacing yourself and focusing on technique.

Image via seksan Mongkhonkhamsao/Getty

There's a fitness myth that says cardio is the only way to lose calories, but that's simply not true. Worse, that mentality might even be holding you back.

"People often focus too much on cardio and the idea of losing weight and burning fat," says Piskin. "What they don't focus on is building a balance in their workouts between cardio and strength training. It is that balance between the two that allows you to see great transformation."

Image via Jose Luis Pelaez Inc/Getty

You may think that purposeful breathing is just a thing that yogis do, but it's super important to get enough oxygen while exercising.

"Feeling dizzy or lightheaded during a workout could mean that you are not breathing correctly and that you are over-exerting yourself. It's a sign that you're not getting enough oxygen to your brain," says Zoeller. Yawning is an early sign that you're not getting enough air, too. It's your body's way of pulling in as much as possible.

The fix is to be purposeful about your breathing and to even incorporate it as part of your workout. For example, breathe in as you lift the dumbbell and breath out as you lower it. Or, breath in deeply for two counts of a run and then out for two.

"Also, work on listening to what your body is feeling," advises Zoeller. "If you begin to feel lightheaded then take a break, drink water, or practice square breath to bring your breath back to a normal state. To execute square breath, take a moment to close your eyes and visualize the four sides of a box. While you practice this breathing exercise, visualize tracing a box with your mind's eye as you breathe. Breath in for a count of four, hold your breath for a count of four, exhale for a count of four, and hold your breath for a count of four."

Image via Richard Drury/Getty

Going into an open gym without a game plan is one of the biggest fitness mistakes you can make, says Piskin. Not only is it overwhelming and distracting, but you'll easily spend a good chunk of your time trying to figure out what to do instead of actually using that precious time you've carved out for your workout.

"Create a weekly gym plan for yourself that becomes standard practice. You will maximize gym time with this approach and see results much faster," she says. "For example, Mondays are cardio either on the treadmill, bike, or elliptical. Wednesdays you do upper body and ab work with machines and free weights. Friday you do a circuit workout between cardio bursts and lower body."

A set plan means more time for your actual workout and better focus during each and every move.

Image via Mireya Acierto/Getty