I once asked someone who was espousing the benefits of spiritual disciplines if they were experiencing spiritual fruit as a result. I think that my question just confused them.
Best selling Christian author Dallas Willard defines a discipline as, "any activity within our power that we engage in to enable us to do what we cannot do by direct effort." Did you catch the word "activity"? I think that Willard's definition is reminiscent of someone who believes that hard fleshly work will produce a spiritual harvest. It reminds me of the thinkings of many humanists.
Sadly many who read, study, fast, pray, tithe, and perform all kinds of religious things do it as a work and consequently really don't develop a character steeped in love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control (ala Galations 5:22-23). Many of them come across as people devoid of these qualities. It is like they believe that grace is initially unearned and unmerited favor but is needed to be earned and merited (by doing religious stuff) after you have received it.
Before you jump to any conclusions I need to say that I am all for discipline and I think that many would do well to discipline themselves unto godliness (per 1Timothy 4:7). The key, in my opinion, is to follow the Holy Spirit's lead in these activities.. let Him (not angry brainy preachers) tailor the discipline to your personality and life.. and when He does you will begin to experience spiritual fruit.. you will love more.. be more patient.. be at peace.. and you will have the self control to discipline yourself in a way that is pleasing to God.