Very good question, and you described the trigger dilemma really well.
A few things come to mind.
The most obvious: avoid the trigger. Duh. A little less obvious: identify the trigger. If you simply say "I am being triggered right now", it loses some power. Not all, but some. It breaks the train of thought about the loneliness and the seeming logic that you HAVE to finish with porn once those triggers show up. It is a bit like hearing a noise in the middle of the night, and knowing the wind is making a tree branch hit the side of the house, and you don't have to wonder if someone is inside.
What is less obvious is that triggers often have triggers, and those triggers have triggers. Take the loneliness. It might occur at the same time each night. That time on the clock can be considered a trigger. Maybe it happens after you catch up on social media. People very often feel lonely after they look at old friends and loved ones seeming to have a lot of fun and bonding while you're alone. It may not be a direct trigger that makes you immediately go to porn, but one that sort of fertilizes the soil and gets you ready. Heck, maybe there's a truly wholesome TV show you're watching on Netflix right now that makes you feel lonely because a character reminds you of someone you loved. It can be the least pornographic thing in the world, but that could turn out to be a trigger.
The only way to know this stuff is to retrace your steps. Ultimately you'll trace yourself back to something that used to seem harmless. The more you trace yourself backwards, the weaker the enemy. Think of it like a video game: you wander into an advanced area, you haven't leveled up enough, and the enemies destroy you. You try again, they keep destroying you. So, what do you do? You find weaker enemies and level up. The stronger ones might still be too tough, so you find some that are a bit stronger and keep at it. You can probably alter some basic stressors more easily than you can deal with the biggest triggers.
Another analogy: when we're in that moment right before we relapse, we're in full on zombie mode. The triggers and auto pilot have taken over. Move backwards, and you're still a zombie, but have some control. Back up some more, and it is more of a hankering than a full on pounding heart ready to relapse. Keep moving back, and you'll find a point where you can say "no, this is not what I want to do right now". Trying to wait until that last minute is too much white knuckling.
An example from my own reboot: Loneliness was a huge trigger for me, too. For several months, I could get through a work week just fine. I was busy, I had a routine, I wasn't thinking about these things that bothered me. Then Sunday hit. I'd go to church in the mornings... I'd see happy couples, families, kids, people being with friends, and it sharpened all of those feelings. Then I'd go home to spend the rest of my day alone. I'd find things to do that I enjoyed, but it still gnawed at me. Those were the hardest days. If I took a deep breath and knew what I'd be going through emotionally before I left for church, that helped a lot. Identifying it early makes a huge difference. I also knew not to do things on those days that might lead to stewing or brooding. It wasn't an over night change, but it did work. I've been off of porn more than two and a half years, so I know it worked. That was definitely the "final boss" of triggers in my addiction.
Some fetishes are super tricky. Some are hard to be triggered by unless you seek them out, but some you can see in G rated areas. Even then, there are ways to avoid it, and there are ways that we might be giving up control without consciously realizing it. Someone with a foot fetish might always walk through the shoe section at Target on their way to the hardware section, even though it is a big detour. They might not realize it until they stop to reflect on it. Maybe someone is cutting shortcuts down a certain aisle at the grocery store because he spotted a muscular woman hanging out in the frozen food section, and his fetish is body building. Consciously he's just trying to avoid the old ladies taking up space in the baking aisle or can't remember if he has enough frozen broccoli for the week, but unconsciously he's up to something else. When he gets home, he's going to want to look up those sites even more. A deep breath and saying "seeing that woman is a trigger" helps.
Last thought: the emotional triggers sometimes need some TLC on an emotional/psychological/spiritual level. Sometimes that means seeking out therapy, but not necessarily. Sometimes it is as simple as acknowledging it. Extreme examples are physical or sexual abuse. Varying levels of emotional abuse are pretty common. But, we all have wounds, and addiction finds those wounds, infects them, and then presents itself as the salve to heal those wounds. Getting a bit of TLC on those wounds can interrupt that cycle.
