1. He is trying to appear strong and in control of his emotion. Someone who would never allow love to make him act unreasonably.
2. He has never been in love, and allowed himself to be vulnerable and needing of someone else. In which case, see #1.
3. He always keeps someone in reserves, just in case the situation with the current interest gets a little bumpy, so he can quickly move on without worry of getting hurt. In which case, see #2.
4. His perspective is completely foreign to me, or i don't understand what he is talking about.
I'm guessing with the whole notion of carrying a torch for a love or getting over them, that it is assumed that one goes from one person being the most important thing ever to not even acknowledging they exist.
Relationships end for many reasons. It can be a matter of compatibility, maturity, circumstance, location, timing, emotional health, or attitude. There are times you can destroy a relationship by neglecting the other person or not respecting them. But there is not one universal answer as to why relationships end, so there isn't one standard process for one to go through to accept that ending.
I can only speak for myself, but the process of ending a romantic relationship can vary greatly depending on the significance and length of the relationship, and generally involves a level of grieving, reconciling how it ended, and learning what I did wrong that led to the end that I might want to avoid, or what I did right that my be useful in the future.
Although a new relationship might remove the sting a little, it doesn't alleviate me from the above task. A relationship that has reached a level of significance to me, remains significant even if I have to move on. It doesn't necessarily burden me once I get through the reconciliation process, but I am able to recognize that it has played a role in getting me to where I am now, and I am able to see how that person has contributed to my life.
With that said, there are people that simply hold no significance. I dated one girl, I can't remember her name, we had fun, she was ok in bed, I can't think of anything worthwhile that she added to my life. She might have not felt the same way, and may have been more disappointed about losing me, but when it ended, it ended for me. Being with her didn't make me less lonely for someone special, didn't make me want to do those stupid things that we do when we are in love, and didn't make me hurt when it ended. At least that one relationship was simple.
There are those that didn't find me significant. I might have thought the world of them, and they didn't hardly notice I existed. I had to finally give up, drop the infatuation, and long after when I was over it, I realized how silly I acted.
Aside from those cases, that is where the simplicity ends.
There are the cases of incompatibility. I know I love the person, and I know they love me, but being with them for whatever reason is a constant struggle. The more we try, the more we draining it becomes. And the sad ending involves knowing neither of us will ever change enough to become what we both need. Although they will probably remain significant once the relationship ends, sometimes they aren't even compatible enough to remain close friends. Despite the fact that I have to draw the line on these relationships, there are still good memories, and a bittersweet realization that sometimes two people just aren't right for each other no matter how much they care.
Then there is circumstance. This is probably the toughest situation, when I know we both love each other and enjoy being together, but for whatever reason know that we can't continue on. There are many reasons for this, and I've often had to resort to picking a date on the calendar, when if the circumstances don't change, I will force myself to move on. I've been pretty good to sticking with this, knowing that it won't do anyone any good for me to just to keep on obsessing on why it didn't work out. Even though deep inside I might not have given up on the idea that it could have worked out if things has been different, I'll still go through the same process, being sad, picking the things that I liked and didn't like about it, and deciding what I could have done better, or what really worked well that I should keep on my list of nice to haves for future relationships.
As far as torches go, I don't think it has to be a romantic relationship for me to find significance it how it impacted my life. Moving on doesn't necessarily mean burning bridges. Not much can be done about compatibility, but sometimes circumstances change. There was one girl that I was close to in high school that we never quite got the chance to date, that I met years later. Even though it didn't work out, we dated for a while and had a lot of fun and good experience that wouldn't have happened if I had just closed the doors, and I'm glad we had the time together. Obviously, it wouldn't be very healthy to be in a new relationship and spending all one's time obsessing about an old flame. So I have had to draw some boundaries where based on the current circumstances I won't cross. But even with that, I still can understand priorities without denying significance of past relationships.
One of my ex-girlfriends who I have remained friends with, and even attended her wedding reception, recently told me that I was the one that got her into graphic design. It's kind of a good feeling knowing that even if things don't work out, I can have a positive role in someone's life.
I know of at least one couple who got divorced, only to later remarry and be happy together. Sometimes circumstances change, and a relationship that ended for some reason, may lead to new relationship worth investing in. One can't stop living hoping this will always happen, and most of the time it probably won't, but similar to how a human resources person will check off "would rehire" during an exit interview, sometimes someone is significant enough where you would give them another chance if things are different in the future.