We have to differentiate between two things: 1- planning and applying the means for achieving success. 2- fortune telling or predicting the future without attributing it to the will of Allah.
It should be clear that it is only Allah Who has the full and accurate knowledge of the future. Even the Messenger of Allah (peace and blessings be upon him) did not know the hidden things except what Allah revealed to him. Allah says, “(He is) the knower of the Unseen, and He revealeth unto none His secret, save unto every Messenger whom He hath chosen, and then He maketh a guard to go before him and a guard behind him.” (Al-Jinn: 26-27) Hence, it is forbidden for Muslims to consult the future tellers or astronomers.
So, the forbidden prediction of the future is that which one assures its occurrence without attaching it to the will of Allah and His destiny.
This is totally different from predicting the results of something taking into consideration that they may happen or not according to Allah’s will and destiny. With good planning and hard word, there is great hope of achieving success. But still there is a possibility of failure to achieve the desired or expected result one hundred percent and even there is a possibility of not achieving this result because it depends on Allah’s will and destiny. Another example is a student who studies well and is keen to attend his class. There is great hope that he succeeds and gets high remarks. However, this is not for sure one hundred percent and no one can predict it exactly because it is only Allah Who knows the unseen. All one has to do is to plan well and take the necessary steps for achieving the desired result believing that it is Allah Who knows exactly that result before its occurrence.
Having stated the above, it becomes clear that the good feeling of achieving a good result in certain field after applying the necessary steps of success is not included in the forbidden prediction of the future.
The forbidden prediction is that which one assures its occurrence accurately in a future time without attaching the issue with the will of Allah and His destiny.