When you watch the UFC, WEC, or other combat type competitions, every fight is set up into rounds.  Boxing has two or three minute rounds and MMA has five rounds.  So, it would be evident that sometimes our training should incorporate this methodology as well.
Train for five rounds while mixing up your routines.  Make sure they are all at different levels of intensities.  This will force your body to adapt to different levels of conditioning, developing you into a better fighter.  It will also prevent your body from plateauing and you from boredom.
Shadow Boxing
This is one of my most favorite ways to train, because I get to throw any technique I know how to do without worrying about hitting something I am not supposed to or being limited to equipment.  It is also free to walk into a park or your backyard and shadow box.  Of course, this should not be the only way you train, but it is an important area of martial arts.
Shadow box for two, three, or five minute rounds based on your current physical condition.  Start out slow by throwing a few jabs, working strategy technique.  This is a simulated fight, so practice blocking, weaving through imaginary shots, move around your imaginary opponent.  Focus on executing combinations such as the jab-cross-round kick combination.  Mix it up and see what works for you.
Make your training in shadowboxing as real as possible.  If you happen to fight for real, what you do in shadow boxing will naturally flow into a real fight.  If you do not make it realistic, you will pay for it later.
Heavy Bag Work
Just like your shadowboxing, do the same thing, but this time on the heavy bag.  Focus on angles, blocking, slipping, and weaving in conjunction with your strikes.  Do not neglect your footwork as you move around the bag.  When striking the bag, mix powerful kicks and punches with short fast strikes.
Defensive Drills
For the third round, you are back to shadowboxing, but this time start focusing on being defensive.  Throw a few strikes here and there at your own discretion but focus on blocks, slipping, and your footwork.  Look for ways to counter your imaginary opponent, and working your way around his strikes.
Power Shots
During this drill, your goal is to try and “knockout” your opponent.  You will be back using the heavy bag for this drill.  Hit the bag as hard as you can, using combinations and powerful shots.  Throw a lot of crosses, round kicks, and other devastating techniques.
Finish Strong
In the final round, hit the bag as fast as you can with as many combinations as you can muster.  This drill is meant to tire you out even more.  Focus on power, speed, movement, with very few pauses in between.
Training in rounds every day in the same way can be tiring and monotonous.  Sometimes, training will require something different where round training would not work.  But as we train, we should not forget to incorporate round based circuit training because this is close to the real thing, and that is what we are training for, training to fight.