Every believer in Christ has at some point in his Christian walk experienced failure. He falls into sin and then asks God's forgiveness. Because Salvation is a life-long process, there is no instant perfection and we all have committed some sin at some time.
"If we claim to be without sin, we deceive ourselves and the truth is not in us.
If we confess our sins, He is faithful and just and will forgive us our sins and purify us from all unrighteousness." (1 John 1: 8-9)
There are two kinds of sin - intentional and unintentional. Intentional sins are those we commit willfully and with choice. We know it is a sin that offends God and we do it, for one reason or another. Then we realize the gravity and effect of the sin in our lives and we repent. We ask God's forgiveness and strive on to avoid instances when we will fall into that sin again.
Unintentional sins are those we do out of ignorance and lack of awareness. I remember a young Christian leader who said that he had a tattoo of "John 3:16" on his arm to show he was a Christian. I told him that the Bible explicitly forbids us to have tattoos or marks in our bodies (Leviticus 19:28). He did not know that and had to have his tattoo erased. Another kind of sin that is unintentional is as ordinary as running a traffic light or parking in "No Parking" places.
Overuse of make-up in a woman is also a sin as the Bible says we should dress modestly and simply, having our inner beauty shine not from outward adornment of jewelry and fine clothes but from a gentle and quiet spirit.
Many Christian women today cause a stumbling block amongst unbelievers because of the way they dress. I remember a tele-evangelist whose wife had a huge coiffured hairdo and thick false eyelashes that made her look similar to a known country singer/celebrity. There was really no difference between her and the outside world. Another was a woman who said she was a Christian dying of cancer, but her last interview showed her with thick make-up and yes, false eyelashes.
These kinds of extravagance and excesses are sins because they already exalt the love of Self. They cause others to doubt our testimony because how we look does not differ from how the world looks. Extravagance clouds our testimony. Sometimes the impression we give the outside world speaks louder than the Gospel we are trying to preach.
The best guide we can have as always is the Bible. Simplicity and modesty is beauty. We are to clothe ourselves with humility, compassion, gentleness, kindness, and patience. What we do and what we wear affects our testimony and if there is anything in these that causes others to doubt our testimony, I think we should get rid of it. God blesses us and we are to show His blessings with humility and moderation. If we do not need it, let's do away with it.
"Therefore, as God's chosen people, holy and dearly loved, clothe yourselves with compassion, kindness, humility, gentleness, and patience." (Colossians 3:20)