If OP changes his mind and starts a new account he still needs to have high activity to reach top ranks of his arena shard and stay there. If he just plays casually, starting over really won't do much good. OP risks ending up in the bottom of his shard with not much chance of advancing since everyone is active on new shards. On his current account he can quickly reach top-1k and not drop, since only the top few hundred are active still.
I believe @littleMAC answered OP's question very well.