Easy answer is practice.
When I first started in Karate, my sensei would just hit my shins w/ his knuckles! Once my speed picked up, he would grap my leg and tap my groin just to let me know that I was "too slow". You should practice kicking and rechambering the leg w/out putting it down. Start with 5 kicks per leg working on getting the kicking leg re-chambered. Use the heavy bag. Do that w/ all your kicks, alternating legs after each set of 5 kicks.
Another trick is to have a partner gear up w/ a hogu and try to catch your kicks. He should not try to block, just catch. You will be surprised how quickly things will change...
