Focusing on "Mind to Muscle Connection" is one of the most important attributes to working out. A lot of beginners neglect this feature because they're worried too much about how heavy they're lifting. That's why you see some bodybuilders in the gym dying out on lighter weights you may typically see a beginner doing. The bodybuilder is focusing on squeezing and contracting their muscles to get full isolation and maximum muscle development, rather than using momentum and other muscle groups to lift the weight up. Anyone can curl a 50lb dumbbell if they bounce with their legs and swing with their back. Your chances of getting injured doing heavy weights is a lot higher and you won't be developing your muscles to its fullest capabilities.
The next time you're doing bicep curls, try doing a lighter weight while focusing on squeezing the muscle group you're working on at the moment.
Example: While performing a dumbbell bench press, focus on going full range of motion and once you hit the apex of the rep try to flex your chest for at least 2 seconds before the eccentric part of the rep (I recommend you start off with a lighter weight to get used to this technique). If you do this technique for at least 12-16 reps and for all of your exercises, I can confidently say that you won't be able to brush your teeth properly for the next few days.