OT/NT God ?!

I know this question has been asked many times before across multiple forums but why does it seem as though the God in the Old Testament and the God in the New Testament have two completely different personalities and ways of dealing with humanity ? OT God seems very wrathful while NT God seems patient, loving and kind . What’s the reason for the severe juxtaposition with our God that is supposed to be the same yesterday, today and forever more?!