If you have ever hit a point in your fitness endeavors where your progress has stalled and won't seem to budge, then you have probably hit a plateau. The best way to plow through this temporary bump in the road is to refrain from getting frustrated, you'll just raise your cortisol levels. Secondly, take this time to re-evaluate your goals and write them down. Keeping a diet and workout journal is the best way to determine where you've been, where you are and where you are going.
Once you've established what you want, change everything you have been doing. Workout on different days and at different times. Get outside on your bike or your feet instead of holing up in the gym. Try free weights instead of machines and stick to the basics over fancy manuevers. You can't go wrong with good old fashioned pushups, pullups and dips either.
Another thing to include in your new fitness program is balance and agility training. Most people don't even bother with this or know where to begin with it, but avoiding it altogether is a major mistake. Tools like agility ladders, cones, tires and the like are easy ways to get some practice improving balance, quickness and spatial awareness. Most people who play sports such as soccer and football benefit greatly from agility training and the skills learned carry over onto the field and can transform an athlete's abilities completely.
Agilty training improves coordination, reduces injury, strengthens the whole body including the core and gets the heart beating fast. When the heart beats fast, sweat pours and fat melts. This is what you want. Get creative and search out ideas for agility, balance and coordination drills on the web or check out some books on the subject. Agility training is fun and challenging as well as something unfamiliar that holds the key to breaking through those pesky plateaus.