How do you know if you truly love someone?

You would know when : It's the most amazing experience in your life. You feel disconnected with everyone around you except with the person you are in love with. He is there in your thoghts and silence. You feel his happiness, his pain, his touch and everything about him is so special even his faults. You would find it in your heart to forgive and explain any mistake that he might do. Also, You feel sorrow in your heart when you need to see him or talk to him and he isn't there for some reason. You feel the need to help him in any way you can.It's painful and enjoyable experience at the sametime if it is true love.