Sometimes what I mean by "clingy" is that I can cuddle forever. It's like a fountain of dopamine and oxytocin that I don't want to clog up.
I'm not clingy in the sense that I'd be a helicopter bf and try to control everything my SO does.
I'd of course be anxious, maybe even romantically jealous, when they are away, because the prospect of losing them would feel stronger, but I'm acutely aware that those are my own feelings, and that there is a difference between my feelings and reality.
Another thing is that, while I would be very hurt if my SO was no longer romantically interested in me, there is really nothing I can do to change how they feel at that time. No amount of arguing, pettiness, or controlling would bring back their romantic feelings toward me. At that point I would focus on moving on and processing the loss.
I would also try to foster enough openness and approachability / availability that my SO would not be afraid to tell me how they feel, nor feel like they are trapped in the relationship. I'd want it so that we can still be good platonic friends, even if we happen to drift apart over time.