“even a recipe for failure of the relationship? And how would the “unconditionally loved” feel when he/she realises that the love they’re receiving is not special to them? “

(Another fitting aphorism: If one in a relationship grows to love (more) unconditionally, and the other stays (more) in conditional love, then someone has to catch up or someone has to stay behind….

To answer this, let’s equate ” special to them ” to refer to their particular form, whether it be physical, mental or behavioural. We say that we love their hair, their humour, their playfulness.
If you identify yourself and others only in tangible forms such as hair, humour and playfulness, then you have no place to receive the formless unconditional love I’ve proposed above.
But wait, you say, of course there is the inner person to love as well. Sure, I agree, but I am answering only in terms of the inner person, and I am discounting the outer forms, in order to make the distinction.
I’ve equated that formless unconditional love as being one end of a spectrum, when it has no such tangible attributes.
Let’s bring ” unconditional love ” down to earth a little, let’s move it along that spectrum to make it more identifiable and tangible, and make it refer to the inner person. Hair, humour and playfulness is over on the right end and out of the picture for this.

(lots of discarded attempts to explain something)

Wow. I had a strong feeling that unconditional love was connected with a specific aspect of the inner person, in the sense of the inner person having less form and shape, and being more attuned to receiving unconditional love. But it seems that I was confabulating. So it took me a while to characterise the inner person, and then identify the two aspects of this inner person. And after all that, neither aspect seems more available to unconditional love. So here is the exploration. As and when I come to a different conclusion, then I will rewrite this sentence and the whole paragraph. Until then, this work in progress demonstrates my dysfunctional mind.

The first is the extension of their (benevolent) features, such as their playfulness, to the inner person. (Malevolent features don’t clarify unconditional love, and are another subject anyway).
These traits or features are based on, or wired to, the persons benevolence in particular, and their make up and identity in general. Sure, loving loved ones and environment amplify such benevolence, but it is still based upon the original person.
So let’s say that love for the inner person (more of the unconditional type) resonates and matches the unconditional benevolence of that person. The main feeling and sense is that neither side had conditions or hesitation, nor did there need to be much choice or alternate awareness.
In a sense, this resonance is undeserved and a predisposition.

The second is where they are more aware of alternatives and choice. This is most apparent and noticeable after a big shift in the person’s life, such as through loss, ‘awakening’, and other circumstances. After such a shift, a noticeable aspect is how much the previous life was assumed, and how it had less existential choice and alternatives compared to after the change.
This expansion of awareness of alternatives, and that any one form of a person is just one of many possibilities, cascades into many other aspects of the new life, including love that is less conditional in having less assumption, form and familiarity.

But as I consider these two again, they both have shape and form, and aren’t inherently associated with unconditional acceptance. Sure, the second has more promise in that the change may cascade further along the spectrum of unconditional acceptance, but there is no inherent dependency or association.

But this second one does leading to metacognition, which in turn leads to meta-metacognition, which is a cognitive route to unconditional acceptance.
The other route to unconditional acceptance is, obviously, your heart and your love.
Both these routes are essential in most people having a mind and a heart.
The mind and cognition gives detail in your life, and your heart and spirit sets the direction, tone, etc.
The heart and spirit can clear and change your mind and cognition, but not the other way around, at least not directly.

Metacognition and meta-metacognition are another chapter, soon.

Until then:

Metacognition is sensing a pattern in things, a model of how they work, a pattern of a mind.

Meta-metacognition is sensing a pattern in the patterns, a model of the models, a pattern of all minds. Sure, some minds have a view that (all) minds need is a big stick and big ruler. But that’s not following the evidence, nor is it based upon the emergent properties of a mind or the collective mind(s).

EsSample’s metacognition is that minds are modellers, a description that has “all feeling wrung out of it” (le).

EsSample+’s meta-metacognition is that identity, which is just another model (but your only and central model) shapes all your other models of this world. This is an obvious truism. It is the truism that is a mega-key to unwinding identity and creating choices. It’s also an obvious truism that is neglected and not part of our ontology.
It is a mega-key that is neglected in the same way the mini-key of “anger is not getting your own way” is neglected. This mini-key can unwind all anger – assuming you sense that the universe wasn’t created so you could get your own way.
It is the mega-key behind Buddha’s “all faculties of sense a manifestation by your own mind. Physical bodies are manifestations of your minds representations of form as subjectively imagined. These manifestations are like the flow of the river, passing from instant to instant.”

If you find that every (instant of every) human human is possible, or at least imaginable, then it’s a bit difficult for acceptance to stop and attach to any one shape or condition – all of them have acceptance. Unconditional acceptance. It’s a bit difficult because the shapes and forms are not only one of many possible and equally valid, but also you could change them in a stroke – literally and medically.
It is this way and being that has the same pattern as unconditional love, and so is more resonant and matchable with unconditional love.