Jannah belongs to unseen world which is yet to be created, and we have been given very limited knowledge about its content and its mechanism based on our limited view of this world, that is why it is known as ‘amoor-e-mutashabihaat‘. Therefore the only certain things are principle statements given w.r.t Jannah and one of such statements is:
بَلَى مَنْ أَسْلَمَ وَجْهَهُ لِلّهِ وَهُوَ مُحْسِنٌ فَلَهُ أَجْرُهُ عِندَ رَبِّهِ وَلاَ خَوْفٌ عَلَيْهِمْ وَلاَ هُمْ يَحْزَنُونَ
Indeed, those who surrender themselves to God and do deeds in a befitting manner shall be rewarded by their Lord: they shall have nothing [there] to fear nor shall they be grieved. (Quran 2:112)
Thus pointing towards the fact that all kind of grief would be eliminated.