The issue here is the level of consent in your will. The fact that you stopped yourself reveals a divided heart. I would say that any attempts to stop yourself are partial consents of the will. The degree of consent is a spectrum. Is it sinful? Yes, every willful decision you make toward evil is sinful. Temptation is simply the urge to sin. Not an ounce of willful choice has been made. It simply looms over us, tempting us to reach up our hand to the fruit.
The sin begins with a decision in the heart, a decision that directs our hand toward the fruit, puts our fingers on the fruit, plucks it, brings it down to our mouth, bites it, chews it, swallows it. Any hesitation or any incomplete act shows varying degrees of partial consent.
You see, the thing, people like to tell themselves that consent of the will is on or off. In doing this, they often see mortal sins where mortal sins don’t exist. Suggest to them that mortal sins are far more rare, and they get mad at you because they like believing they’re in a constant battle with mortal sin. When they go through a long period of not crossing their personal line, they feel proud of themselves and superior to others.
The line does two things. By being exclusively focused on mortal sin, venial sins become the tolerable sins, the ones you can continue to indulge in. Afterall, it’s hard enough to avoid the mortal ones, right? Who has time to focus on the venial ones? But in actuality, our attitude toward sin shouldn’t be like this game. We should seek to be as holy, choose what we’re best able to choose in every moment. Our choices will continue to be imperfect, but we must pursue holiness.
As such, when it comes to pornography, what you need to work on in your spiritual journey has to do with your level of slavery to the sin. Are you heading toward a greater level of self mastery or not? Are you progressing more and more away from sin? And are you ensuring you’re focusing on the particular virtues God wants you to work on? Sometimes we can obsess over certain sins to avoid dealing with the larger ones.