Scepticism and doubt are useful faculties in decision-making processes. They temper over-enthusiasm and are the antidote to wishful thinking. When deployed constructively with reason, they are helpful.
But they must be not allowed to be constant companions, riding shotgun, or they sew every project with fear and misgivings and undermine confidence in oneself and in God.
Activate them when necessary but put them away when their job is done.