that is why they put the effort in! Just like serious athletes practice for hours every day - they aren't typically perfect in their sport from birth, they have to work to improve, to achieve their ideal.
You've really got it backwards if you think Christians are supposed to be perfect. The reason they are Christians is because Jesus is the intercession (?) between the sinner and God. Christians believe we are all sinners, thus if we believe in Christ, we can have the true relationship with God, because Christ died for our sins.
Whew, I hope I stated that correctly. I am not active in any particular 'faith'; I am spiritual but not religious. Please straighten out what I've written if you know it!