While performing your worldly duties, repeatedly remind yourself that God is with you. Practise rupadhyana and visualise, "Yes, He is in front of me." There are two benefits to this. Firstly, you will progress in your devotional practice. Secondly, because you experience that God is personally present with you, you will not be undisciplined and thus will be saved from committing sins. If the mind is given the slightest freedom it will naturally be attracted towards the material world.
Therefore, you should always feel your worshipped form of God to be personally present with you. You should keep practising this, even while performing your worldly duties, even if it is just for a second or two at a time. Rupadhyana is so important that without it you will not be able to quickly experience devotional bliss through the chanting of Shri Krishna's names, qualities, pastimes, and so on. When a devotee does not experience any special bliiss, he will become tired of his devotional practice and will finally stop. Rupadhyana is the only means to restrain the fickle mind. The mind has been accustomed since time immemorial to desire forms and qualities. How could it possibly develop strong faith in the divine name in the earlier stages of devotional meditation? Therefore, you should pay great attention to rupadhyana.
Jagadguru Shri Kripalu Ji Maharaj
An excerpt from Rupadhyana - Loving Remembrance, the English translation of Rupadhyana, p. 8-9