Saying you know how to defend yourself or calling yourself a fighter, but never having the experience fighting is hypocrisy. Training videos, heavy bag drills, or any type of conditioning is important, but not enough if you truly want to be capable of protecting yourself.
The more you spar someone, the better you will become. In the beginning, it is appropriate to spar someone at your own level. The more advanced and experienced you get, you should start to spar those who are better than you. If you are a blue belt and spar a black belt, you will see major dividends in your sparring capability than sparring someone at your level.
I can relate if you do not have someone else to spar with. Maybe you do not have the money to invest in a gym membership. Instead, take the training you have from hitting focus mitts, heavy bags, etc., and get some friends that are interested in training with you, and spar with them. Just make sure you are wearing the appropriate sparring gear to prevent serious injury.
It is not enough to hit heavy bags or training equipment to become proficient in fighting. It takes sparring experience and development to be ready if your life depends on it. Join a gym for a month, and gain some experience. Find friends who want to spar and train with you. You can join us at Fighters4Christ and learn how to fight for less than you would pay at a gym. Just as with anything else, experience only comes from application.