One person gets your full attention
Because your Mercury reads in Leo and applies it to the 7th house, your warmth is not distributed evenly across everybody but aimed, generously and completely, at whoever occupies the central seat. Being on the receiving end of it is a considerable experience.
It is genuine rather than performed. The complication is that the same intensity applies to being disappointed by that person, and there is no small version of either.
The pair has to look right from outside
How the relationship appears to other people matters to you more than you would readily admit: the impression it makes, whether it is admired, whether the two of you are enjoyed as a pair. That is worth being honest about rather than defending. The risk is staying in an arrangement that photographs well, so check occasionally whether you would keep it if nobody ever saw it.
The disagreement acquires an audience
Even a private argument gets conducted as though somebody were watching: the speech, the position taken, the retreat that would cost too much face. That turns a small matter into a set piece neither of you can leave. Concede early and warmly, out loud. It reads as strength to the person opposite and it removes the entire mechanism.
You will not say that you need reassuring
Asking to be told you are valued feels to you like forfeiting the thing you were asking for, so instead you go quiet and hope it is noticed. It is not noticed; it is filed as coolness. Ask plainly. Nobody has ever thought less of somebody for saying it out loud, and the alternative you are currently using has never once worked.
You make the other person more themselves
Your attention has a genuine effect: people become funnier, braver and more interesting in your company because you are visibly enjoying them. That is a real gift to give somebody daily. Notice that it also makes you responsible for the atmosphere, and that on the days you have none to spare, the relationship has no other engine running.
Being unappreciated is physically flattening
A long stretch in which the person closest to you says nothing warm registers in your body rather than your mood: low energy, poor sleep, an unexplained heaviness that lifts entirely after one good conversation. That is not vanity, it is how your system is wired. Treat a prolonged absence of warmth as a real drain and address it directly rather than waiting for it to correct.
Say it, and keep saying it
Both halves of this apply: you need to be told and you are very good at telling. What tends to lapse is the second, once the relationship is settled and the effort feels less necessary. It is exactly as necessary. Say the specific admiring thing weekly, out loud, and you will find the same thing returning to you without ever having been requested.
You are better as a pair than alone
In company you and your closest person operate as a unit, and it works: the shared story, the double act, the sense that arriving together improves the evening. That is genuine and it can become a costume. Go to one thing alone occasionally, so that the friendships have their own footing and are not entirely mediated through the pair.
Give your partner the credit publicly
In any working partnership your instinct is to take the visible half, because you are better at it and it is where you are comfortable. Over time the other person becomes invisible and eventually resentful. Name their contribution specifically and in public, repeatedly. It costs you nothing you will actually miss and it is the single thing that keeps a working pair together.