Healthy appreciation, or lust?

Where is the line between a healthy appreciation for Gods creations, and lust?

Two scriptures came to mind: 

Philippians 4: 8: Finally, believers, whatever is true, whatever is honorable and worthy of respect, whatever is right and confirmed by God’s word, whatever is pure and wholesome, whatever is lovely and brings peace, whatever is admirable and of good repute; if there is any excellence, if there is anything worthy of praise, think continually on these things [center your mind on them, and implant them in your heart].

Psalm 19:14: Let the words of my mouth and the meditation of my heart
Be acceptable and pleasing in Your sight,
O Lord, my [firm, immovable] rock and my Redeemer.

Appreciating a good looking man and lusting are two different things.  Appreciation is simply that, appreciation.  Lusting get's to the direction of sexual meditation. So it can be, you see the fine man and acknowledge that he is good looking! Noting wrong with giving God His props! But, now you start to envision yourself in sexual situations, fantasies and moments with that same guy. That then becomes lustful.  The thing about it is that the things we meditate on are things that we desire.  The more we meditate on them, the more we will desire to act upon them.  

Sex is a wonderful act and exchange. Let's be very clear on that! But, if we are sexually fantasizing on these good looking men, restraining ourselves from them in real life will be challenging.  

You have to pray and ask God to help you with some discipline and with meditating on other things. Neutral things.  Be careful what you watch and listen to, that has a way of affecting the thoughts as well. You don't want to make waiting for sex in marriage harder than it needs to be.