What does reliance on or trust in God mean?
Such reliance upon God should not be misunderstood: it does not mean ignoring cause and effect completely. It means, rather, that one should think of causes as a veil to the hand of Power: in observance of them one seeks to act in compliance with Divine Will, which is a sort of worship in action. That desire and seeking is, however, not sufficient to secure a particular effect. The achievement, we must understand, in accordance with right belief, is to be expected only from God, the All-Mighty: we believe in Him as the sole producer of effects, and therefore we should be always grateful to Him.
source
http://www.islamanswers.net/thanksgiving/reliance.htm