Allah U promised to grant them guidance, which is the showing of the straight path and the guidance to the path of the Prophets and Messengers.
Although Allah U says: ﴾اهْبِطُوا﴿ “Go down”, He also reassured them by saying:
﴾فَمَنْ تَبِعَ هُدَايَ فَلا خَوْفٌ عَلَيْهِمْ وَلا هُمْ يَحْزَنُونَ﴿
“whoever follows My guidance – there will be no fear concerning them, nor will they grieve.”. This means that their descending to the Earth was not the end of them. For whoever follows Allah’s guidance while on Earth, will have no fear, nor will they grieve.
The difference between fear and grief: Fear is towards something which will happen, while grief is towards something that has already happened.