"May Allah increase you in keenness, but do not do this again."  

أَنَّهُ دَخَلَ الْمَسْجِدَ وَالنَّبِيُّ ﷺ رَاكِعٌ فَرَكَعَ دُونَ الصَّفِّ فَقَالَ النَّبِيُّ ﷺ زَادَكَ اللَّهُ حِرْصًا وَلاَ تَعُدْ  

"The Messenger of Allah ﷺ prayed one day then left and said: '0 so-and-so, why don't you improve your prayer? Shouldn't the one who is praying reflection how he prays it for himself? I can see behind me just as I can see in front of me."'  

صَلَّى رَسُولُ اللَّهِ ﷺ يَوْمًا ثُمَّ انْصَرَفَ فَقَالَ يَا فُلاَنُ أَلاَ تُحَسِّنُ صَلاَتَكَ أَلاَ يَنْظُرُ الْمُصَلِّي كَيْفَ يُصَلِّي لِنَفْسِهِ إِنِّي أُبْصِرُ مِنْ وَرَائِي كَمَا أُبْصِرُ بَيْنَ يَدَىَّ