Q2. God purposely created us with a good and natural sexual desire. How do we distinguish between that God-given sexual desire and forbidden lus+?
Any **** or longing outside of the marriage relationship that is allowed to persist is a dangerous place to be. God has promised us the Holy Spirit as guide and counsel and this would not be a place that He would lead the Believer into.
The Believer has some responsibilty in this 1.) to pray and give the feeling over to God - make him the desire of your heart 2.) Like Joseph get yourself away from the object of ****. Don't even go back to get your coat.
2 Corinthians 10:4 (for the weapons of our warfare are not of the flesh, but mighty before God to the casting down of strongholds),
5 casting down imaginations, and every high thing that is exalted against the knowledge of God, and bringing every thought into captivity to the obedience of Christ;