Talking to yourself isn't an abnormal thing - David talks to himself continually throughout the Psalms. Our self-talk, however, must be in line with what God thinks about us, and with what God thinks about the world. Regardless of what you feel, it is Biblical to ask yourself, "why are you so downcast, oh my soul?", and to remind yourself "bless the Lord, oh my soul". Let God in to renew your mind, and begin to talk to yourself in a way that will glorify God and lead you to a fuller life