Both of them (theory and practice) joining together become complete in Bhakti tradition. But just with these two, the goal of Bhakti is not reached. Atmarati or Self-joy is more important than these two things. The role of theory and practice are only to give us that Self-joy.
Atmaratyavirodheneti Sandilyah. (18)
Sandilya goes deeper, widening the scope of Bhakti than Vyasa and Garga by
proclaiming -"Quality of Bhakti is any action that never goes against the Self-joy". A long explanation is needed.
The two aspects of Bhakti - performing puja to the Lord and saints and hearing the stories of the Lord and saints immerses us in satisfaction,
peace, pure love, fulfillment and calmness, which are the very nature of Self. By performing Bhajan or puja sincerely, we remain in tranquility
at least for a fraction of second. This calmness appears to be a mental faculty. But in reality it is the very nature of Self. Remaining thus in tranquility, the mind feels highly fulfilled and complete. This is purification of the mind. This can be anybody's experience who sincerely engages in these sadhanas.
Mundakopanisat (3.1.4) points out the seer as atmakrida atmaratih - 'Self-enjoyed; playing with the Self', we see these two sadhanas wonderfully
practiced in the tradition of visistadvaita. Ramanuja propagated these two concepts to enable the devotee to offer himself totally at the feet of the Lord.