Moses told God, God I'm not a good speaker as a matter a fact I stutter and I slur my words. Moses didn't believe in himself maybe it had to do with being put in a stream and floating off all alone who knows! the Reality is we all have been abandoned or let down in some way that has affected us.
Past hurts or let downs can easily affect us in the present if we let them. Just like Moses we can underestimate what we can do, better yet what we can do for God. Moses not only had disbelief in himself but he forgot or over looked who was telling him to speak. Immediately after he said God I CAN'T! God himself corrected him when he said didn't I make man to speak and to listen?! One thing we have to remember is that anyone in Christ is a new creation all the old has become new. The past must stay in the past! our weaknesses must propel us to success and accomplishment now that we know it's God that has called us!!