He must plan with caution, and he must put his trust in Allah (GOD).
To trust in Allah (GOD) without taking appropriate measures, i.e. without making an effort to achieve one’s goals, is a contemptible misunderstanding of the religion.
And to take appropriate measures without trusting in Allah (GOD) means that there is a defect in one’s faith in Allah (GOD).
An One poets said:
“The slow cautious person will achieve part of his goals, While the impetuous hasty one will often fail.”
By being circumspect in your affairs, you will not have acted contrary to your belief in preordainment, but rather, you will have implemented a fundamental part of it.