It's very important to know yourself. Who will if you won't? And why not, right? If you know yourself you'll be able to identify what's your strengths and weaknesses. You'll be able to overcome your problems because you know to yourself that you are good at this or you are bad at this. It will be easy for you to accept the things that may come in your life.
And knowing yourself is essential to know your strengths and weaknesses. If you know yourself right, you may get the correct information as a basis for any problems you have. You may know yourself by getting information from your closest and trusted friends or your family. On my opinion, the people who you are with for so many years may have known you for who you are and the reasons why are you like that specially your family. They have known your actions, you attitude, you perspective and your plans. Those things may have something to tell about you.
Sometimes you just have to be true to yourself. You just have to follow your heart and your mind. You may gather opinions from your friends and family but what makes you who you are is what will you do or what will your actions will be. And if you know yourself, you'll be able to showcase what you are good at. If you know to yourself that you are good at that it will boost your confidence to do good. And also, if you know that you are not good at something you can do something to improve that.
It's just a matter of being true to yourself. Live life. Spread the Light! :)