How did Krishna forget the Bhagavad-gita, as he states in the Mahabharata?

From: vajra nrshima das

pji my Question is in mahabharata (ashavemad parva)Section 16 XVI Anugita Parva (mbh 14.16.431) . when arjuna asked krishna plesase again tell me  the knowladge of gita which you have spoken in battlefield because i have forgotten that , in reply of arjuna’s Question lord krishna said even i have also forgotten that knowladge i can’t tell you again because at that time i was in yoga but now i can’t .

now the Question is how can krishna who is lord himself forget that gita ?

thanks