Lust is a sin and we all commit it. If you are looking for biblical justification for lust; there is not one.
Take religion completely out of the equation; humanity is designed where sex plays a significantly more emotionally important role than it does in the animal kingdom. We are designed to enjoy it, unlike most of the animal kingdom, we are designed to feel jealousy, passion, love, lust, all from that act unlike the animal kingdom. It’s hard to argue that, FOR THE MOST PART, we are wired to want to find someone that we are compatible with; someone that satisfies our needs and is committed to us.
Bringing God back in; His plan for us is to be fruitful and multiple. In the Bible he lays out His guide to the perfect relationship; sex is very emotional, God says to wait till you find the right person and that’s when you should do it. Anyone that has had multiple sexual partners has probably felt the feeling of regret after the relationship has ended. You can also probably see that when sex is involved it’s a more difficult of a break up because of the shared connection. Those that have had one night stands probably can relate when I say that the lack of emotional love can be taxing sometimes when it comes to sex. Either way sex is an emotional thing and if you follow Gods plan there is a less of a chance to get hurt if you wait for the right person and move into a Godly marriage. Those that wait, FOR THE MOST PART, in a happy Christian marriage don’t regret waiting.
Also sex is a dangerous thing to let control your life. If you are looking for loop holes it’s an idol in your life. If you are this focused on sex you are not going to be able to focus on what you need too.