To adhere to legalism is to believe that the Cross was either unnecessary or insufficient (Gal 2:21, 5:2). That is an accurate interpretation of your motive and actions, even if you still ascribe mentally to the necessity of Christ’s sacrifice. In our legitimate pursuit of obedience and maturity legalism slowly and subtly overtakes us, and we begin to substitute our works for his finished work. The result is either arrogance or condemnation. Instead of growing in grace we abandon grace. That was Paul’s assessment of the Galatian church when he wrote, “You who are trying to be justified by law have been alienated from Christ; you have fallen away from grace” (Gal 5:4).
CJ Mahaney, http://2s7w.sl.pt