We say in sha Allah, not because we are weak minded, doubting whether or not we will be able to successfully reach a particular goal. Nor do we believe we need to appease a narcissistic God, who will not stand for his creation ignoring his dominion over this world. When we say God willing, it is because we acknowledge our desires do not live in a vacuum, but are part of a grand river, flowing towards a point on the horizon, past which we mortal humans can not see.
Towards a Horizon
Khadim Zaman's Blog 