In The Necessity of Prayer E.M. Bounds writes,

Here, let it be said, that no two things are more essential to a spirit-filled life than Bible-reading and secret prayer; no tow things more helpful to growth in grace; to getting the largest joy out of a Christian life; toward establishing one in the ways of eternal peace. The neglect of these all-important duties, presages leanness of soul, loss of joy, absence of peace, dryness of spirit, decay in all that pertains to spiritual life. Neglecting these things paves the way for apostasy, and gives the evil one an advantage such as he is not likely to ignore.