A person that thinks in battle is slower than a person who reacts in battle. Reaction is a must it is a part of being successful in a fight and is the most important thing next to your skills and strengths. There are many ways to increase your reaction ability using other people and equipment. No one should have thoughts running through their mind it can defeat your reaction and you could get hit by something because you were not aware.
If you have a speed bag then you have a good peace of equipment that can help increase this ability. The speed bag is the most useful thing to build your reaction because of it's fast movement it will force you to move faster. You should combine any useful striking techniques and put them in a combination with footwork and avoiding skills like in boxing so you can get the most out of using a speed bag. You may think that having another human around sparring with you can help your reaction better than a speed bag maybe if their fast and had a lot of energy.
If you have a tennis ball, and extra shoe strings keep them you can create something very useful. Another way to build your reaction is to hang a tennis ball 2 or 3 feet away from a wall. Use whatever is necessary to build this ability their might be a day where you may need it.