As a married, expectant dad, I can tell there is a clear difference between ordered love and lust.
Lust desires sex itself - while Aquinas categorized it as “love excessive” it is really love misfocused because it is self-centered, looking upon the sexual gratification of the self rather than some higher purpose.
Lovemaking that focuses on the union with your spouse is not lust. Lovemaking that focuses on you reaching your own satisfaction is lust.
Outside of the bedroom, lust has a wider scope. With your spouse, desiring to give him or her joy and to make love to him or her is not lust because that is proper (and indeed, desired by God in your relationship). With anyone else, sexual thoughts are ruled out. There is no justifiable reason to entertain sexual thoughts about anyone but your spouse.
Being human, I know thoughts pop into my head - the difference is whether to refute them, let them pass or to dwell on them. Seeing a beautiful woman makes me smile, and I thank God for bringing such beauty in the world. But to go farther than that is lustful. For a man to picture a woman naked is as sinful as him dropping his pants and masturbating - it’s only a difference of degree. As soon as you use that person for sexual means in any form, you are lusting.
So you’re out on a date with someone you find very attractive and you kiss at the end of the night. That’s not inherently lustful - the kiss is a token of your affection for one another, and so long as it remains proper, affection is not lustful. By the same way, when I kiss my wife (and she’s a wonderful kisser) I’m not immediately drawn to thoughts of the bedroom - so it should not be that you enjoying a kiss with your date leads to something else. That kiss satisfies a desire to be closer to someone, and it is not an inordinate desire. Likewise, when you hug a friend of the opposite sex, you’re not seeking to rub bodies against each other, but rather share an embrace - and you know there’s something so emotionally comforting to getting a great hug when you need it, and it is so distinct in feeling from a kiss - even a non-lustful purely affectionate kiss - that it should need no further explanation that affection can remain proper.
And for a man to get aroused - well, that’s not rocket science. We can get aroused pretty inconveniently. The physical mechanism is not very discriminating and so should not be obeyed. True arousal takes place in the mind - and so this is where lust occurs. BTW, I’ve heard that recovering sex addicts take to sniffing vinegar as a means to keep physical symptoms under control, while mental control requires self-control.
I hope that helps. Keep focused on purity, keep affections proper, and keep prayer in your relationships and you should not go astray easily.