My Elect Brothers and Sisters; Why are you Reformed?
Give us your testimony!
Because the Bible beat me into submission until I cried "uncle".
Been a Calvinist (of varying stripes) ever since.
Why am I Reformed?
It is the assurance that I was, am, and forever will be, His. It is the knowledge that I am a sinner and yet am firmly in the Creator's grasp. It is that he uses me for his own Glory.
I remember specifically trying to witness to an atheist friend of mine. I was laying out the general scope of redemptive history and trying to explain the gospel to him. I had composed a lengthy email to send to him and wanted to run it by my mother first since I knew she had been to seminary (I wanted to make sure I wasn't missing anything). After she read a particular part about it, specifically the part having to do with "love and free will" she said I might want to take a look at Romans 8 in light of what I said. Now, mind you, I had not studied a lot of theology. I had read through most of the New Testament and had a basic understanding of the Gospel. I read Rom 8 and was confused. I thought "this can't be right...how is it fair for us to be predestined as to what we believe?" I firmly believed that the Bible was the inerrant Word of God, so I knew that what was written had to be the truth. So, I set my mind to work and came back to my mother. I had it all figured out. You see, God could see ahead of time who would choose Him, and so just by the very act of creating them (and thus setting into motion the cosmic chain of events leading up to that choice) He was predestining them. I was rather proud of myself for being able to grasp such a difficult concept. Mom told me to read Romans 9.
I felt like Paul was speaking directly to me, answering each of my objections as I brought them up. I tried very hard to come up with a way to reconcile Romans 9 with my preconceived view, but I couldn't find one. I spent a great deal of time reading through the New Testament, particularly the Epistles, trying to find something that would "explain away" these passages, but all I found were more passages along the same lines. Acts 13:48 hit me very hard. So did John 6.
I finally realized how futile and vain my efforts were, and came to the conclusion that I had no choice but to embrace what I read...that God is sovereign over men and ultimately decides who is saved and who is not.
This experience lead me to spend more time in the Word and more time reading other works. Eventually I found out that the term commonly used for the doctrines I was discovering was "Calvinism." I continue to this day to find more and more in the pages of Scripture as I discover and explore the holiness of God as revealed in His Word.