Lets say that i dont feel guilty of an inmoral sin
I get the sense that you are basing God's view of it on how you feel He will feel. Going ahead with something because you don't feel the guilt.
It is good practice to do some things out of conviction, rather than feeling. When you are a missionary, there will be rejections that will make you feel like quitting, uncomfortable housing that will make you sleep poorly, people who don't appreciate your work both there and at home. If you allowed your feelings to keep you going, you would never make it off the plane.
This is a good time to start self-disciplining your mind. Look at the allover way you approach life, and see how God can work through you now, for His good. Try fasting. If it's hard to do this on your own, put yourself into a situation where others help you understand self-control... like martial arts, boot camp, or other endurance training.
Just something that gives you the jump-start to be able to stop yourself when your brain battles your feelings, your soul battles your brain, your body battles your faith.