You were so afraid that your only concern was to flee, by climbing the mountain, without paying any attention to the Prophet who was calling you back. God then made you to worry about so many things [such as the possibility of your town being destroyed by the victorious army (outnumbering the population of the town), the loss of your fighting companions, the rumor of the death of the Prophet, etc.] so that you may learn a lesson and not to grieve for a loss in the future. Know that God is fully aware of what you are doing.