Don't be Sad
Plan your affairs and take proper precautions
When a Muslim sets out to do something, he must do the following: he must plan with caution, and he must put his trust in Allah. The Prophet (bpuh), who was protected by Allah and who had stronger trust in Allah than anyone else, wore armor in battle. A man asked the Prophet (bpuh), "Should I tie my camel to the post or should I put my trust in Allah?"
The Prophet (bpuh) said,
"Tie it up and put your trust in Allah."
When you take appropriate steps to reach your goal, and when at he same time you put your trust in Allah, you have implemented two important principles of Islamic Monotheism. To trust in Allah without taking appropriate measures --- i.e. without making an effort o achieve one's goals --- is a contemptible misunderstanding of the religion. And to take appropriate measures without trusting in Allah means that there is a defect in one's faith in Allah.
An Arab poet 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 pre-ordainment; but rather, you will have implemented a fundamental part of it.
(And let him be careful….) (Quran 18: 19)
(To protect you from the heat [and cold], and coats of mail to protect you from your [mutual] violence.) (Qur'an 16: 81)