A small example can be given in this connection. Just like a father. He has given birth to hundreds of children. That does not mean the father is finished. These children is expansion of the father, but father keeps himself as father. So in this way He is Vāsudeva, means He is present everywhere. He says in the Bhagavad-gītā, sarvataḥ pāṇi-pādaṁ tat: "He has got His hands and legs and eyes everywhere." Because the part and parcel expansion of God, either viṣṇu-tattva or jīva-tattva, they are everywhere.
Besides that, God is existing in everyone's heart as Supersoul. So the Supersoul is giving direction to the individual soul. Therefore, in the Bhagavad-gītā it is said, sarvasya cāhaṁ hṛdi sanniviṣṭaḥ. Hṛdi means in the heart. "I am situated in everyone's heart." Mattaḥ smṛtir jñānam apohanaṁ ca (BG 15.15). Because God is situated within my heart, therefore He is giving me direction. So our remembrance and forgetfulness is due to God.