Every Christian is a Christian missionary, no matter what sort of work they do. We are all called to share the light and love of our wonderful Saviour with the lost people of the dark world.
Now, some people think that they cannot and should not be in any direct mission work for God, if they are struggling with wilful, known sins.
It is true that, obedience to God is absolutely necessary for a God honouring Christian life and ministry. However, nobody is perfect. We all sin, whether the sin is considered to be big or small. There is no great Christian minister in the world, who never did any sin. We all sin wilfully, because we know that it is a sin, but we still do. Whether it is anger, pride or irritation or procrastination or negligence or idle talk, we all sin. Our sins may be different, but we all struggle with sin and we wish that we don't. The apostle Paul felt the same.
“For the good that I would I do not: but the evil which I would not, that I do.”
Now, should I wait until I get rid of all the so called big sins I know, before I share the Gospel with someone or teach the Biblical truths to others? In that case, we are all going to wait forever. Nobody is going to be absolutely perfect on this side of heaven, but we are all supposed to be striving for perfection. The well-lived Christian life is a life of progression towards more Christ-likeness.
The devil is extremely intelligent. When you are tempted to sin, he tells you, "this sin is okay. Everybody does it". And when you try to do something good for God, he says, "You are unworthy to do this ministry or teach others because you committed that sin that day". Remind yourself of what God's Word tells you. When you are tempted to sin, you should say "No" and we you are prompted by the Holy Spirit to do something good, you should count yourself worthy, because God counted you worthy.