You go at a relationship the way you go at a build
You approach a partnership the way you approach anything worth having, which is as a structure to be built and maintained. Mars in Capricorn in the 7th house makes commitment a serious undertaking rather than a feeling, so what you offer somebody is a durable arrangement rather than an intensity.
The sign is why the offer is reliability and the house is why it lands on one person. That produces partnerships that survive conditions most would not, and a specific difficulty: what holds a thing together is not the same as what makes it worth holding, and only one of those comes naturally.
Assessed for whether they would last
Your criteria for a partner are about durability rather than excitement: how they behave under pressure, whether they finish things, what they are like when money is short. That is unromantic and it has an excellent success rate. Add one question about whether you enjoy them, because it is the one your instrument does not measure.
Conflict administered rather than had
In a disagreement you become measured, factual and faintly managerial, which stops things escalating and prevents anything at all from being resolved emotionally. A partner ends up arguing with a process rather than with a person, and the process is always going to win. Say the unmanaged version once per row, even clumsily, even at the cost of the composure. Competence was not what was wanted in that particular five minutes and supplying it is what makes the row recur.
Commitment that outlasts the reason for it
You will stay through a great deal, on principle, and staying is a virtue right up until it becomes an inability to conclude that something has ended. Set an annual review with yourself, on a date, and ask whether you would choose this from the beginning. Asking commits you to nothing and not asking has already cost years.
The offer nobody thanks you for
What you provide is stability, and stability is invisible while it is working. A partner may genuinely not know what you carry, because none of it is dramatic and none of it fails. Describe one piece of it out loud a year. Not for credit, but because the arrangement is otherwise mistaken for a natural condition.
Say something unearned and unhelpful
Your affection is delivered as effort, and everything you offer can be justified by its usefulness. What has never been supplied is the pointless remark: the compliment about nothing, the message in the middle of a working day, the thing said purely because it was felt. Send one this week and do not attach anything practical to it.
As a couple you are the ones who host
Other people's arrangements run through the two of you: the meal at your table, the group that meets where you are, the plans that only exist because somebody organised them. That is a role you took on without discussion. Ask your partner whether they wanted it, since it is very likely they were recruited rather than consulted.
A partner who will still be there in year twelve
You choose working partners on staying power rather than on brilliance, and the ventures you have been part of are the ones that survived their dull middle period. That instinct is correct and it makes you slow to enter anything. Say plainly at the start what timescale you are thinking in, because somebody expecting a two-year arrangement and somebody expecting fifteen will not discover the mismatch until it is expensive.
Two sets of obligations, both accepted
You take on a partner's family duties as readily as your own, and the total is now considerable and was never added up by anybody. Nobody imposed it; the obligations simply accumulated one reasonable request at a time. Count the annual hours once, with your partner, and decide together which of them continue.
Chosen, rather than merely honoured
Your capacity for commitment means an arrangement can run for decades on obligation alone, without anybody checking whether it is still wanted. That is the risk specific to being this reliable. Say out loud once a year, to the person, that you are choosing this. It changes what the arrangement is for both of you.