According to radical behaviorists "all of our actions are products of preexisting causal influences." For those who belong to this group, free will is an illusion because people are more heavily influenced by the situational factors that trigger them.
So then were does personality play into this?
Decision making can be daunting, but what if we really don't make the decisions and our paths have already been chosen for us?
Well radical behaviorists believe our personalities are bundles of habits acquired by classical and operant conditioning - so really personality to them doesn't cause behavior or factor into decision making, but really, personality is made of behaviors.
So, given this way of thinking, decisions aren't so much as made, but are results of our bundled personalities - so personality is wholly influential on decision making, even if they aren't actual decisions but just products.