After you’ve started training martial arts for a little while and you've built a foundation and are becoming more comfortable with some techniques you’ve learned, the next step would be to start sparring.
Sparring is a great tool for understanding where your strengths and weaknesses may lie, and is the best representation of a real fight. It is the stepping stone to amateur or professional fights and competitions. Now, many students who first start sparring specially with another sparring partner will find themselves blinking, freezing, and flinching a lot. It's extremely uncomfortable getting in someone's face and most people are scared of getting hit. Sometimes stepping into sparring class, people will forget all the techniques they've worked tirelessly to learn. This is one of the biggest problems, and it's usually because the martial artist hasn't practiced their techniques enough.
The obvious answer that most coaches provide is to just keep sparring and in time you will get better. That's fine, and like most things in life, it will take time. But the fastest way to get better is by... DRILLING. This key aspect of training is usually underemphasized by coaches and gym owners, who put a lot more emphasis on conditioning.