You can't break the habit. You pick up a tablet or sit down at your computer desk and start twitching in your pants. You're subconsciously becoming aroused. The habit is strong. You might not even notice what's happening to you until you leak a little pre cum. You weren't even thinking about watching porn but your body is so conditioned from the correlation between the screen and the stroking.

Because all your little quickies turn into hours lost scrolling through clips, looking for that perfect fantasy. Stop fighting the flow and give into it.