You know that is actually a good question. I have seen lots of people who call themselves Christians but feel no different inside than when they weren't Christians, they find being a Christian to be boring and they just feel like their going through the motions.
Before I was a Christian I wanted to be saved but I never made that connection with God, no one had ever taught me about this connection I just somehow knew that as a Christian there has to be an actual connection an actual relationship I wanted the real thing not just some religion to follow.
The thing is though i never could seem to make that connection and deep down I knew why, I valued my video game addiction more than him, he was not number in my heart and in my life and it wasn't until I had enough of my lonely and sad existence that I was more than willing to toss everything in my life even accept death itself just that I could have him. I actually was in tears and begged him to take everything I own and told him I don't care if you even take my life as long as you come and live in my heart. My life was trash and worthless in my eyes and only then was that connection made.
Ever since that day that bond has been growing and the connection is just real to me as it was on that day, and I fell madly in love him I suddenly had this zeal and passion for him I am not a passionate person and yet I would have gone through absolute hellfire before I would give up my love and bond with him. This is not normal mind you even for the average believer such a fire as that is rarely seen not that I myself can boast in any way nor was it any of my own doing but on that day a covenant of the hearts was made and infused in a blazing fire that to this day fills me with life and is seen by others that I even just meet.
The source of such a flame is the bond he and I share we don't go through the motions or do the church act we get to know each other we speak all the time about anything we crave being with each other and enjoy each others presence I mean I can have the worst day ever where everything that could have gone wrong went wrong but if at the end of the day he and I can have five minutes of just being together then the entire day was worth it to me.
For me this is how I know