Why is there so much emphasis on repentance in the Orthodox Church?

Some of the first words that Jesus spoke are recorded to be, “Repent, and believe in the gospel." (Mark: 1:15). Many Christians today seem to focus exclusively on “believe”, without remembering that Our Lord says first we must “repent”! Just as His command to “believe” is not understood by Orthodox Christians to be a one-time act, in the same way Orthodox Christians understand repentance to be a continuing command as well. The Orthodox attitude towards spirituality, its very “ethos”, reflects the attitude of the tax – collector, the sinner, as extolled by Christ Himself (Luke 18:10-14). You will hear a lot of “Lord Have Mercy”, in Orthodox services!