The feeling is uneven. It lasts if you keep adjusting, not if you wait to match.
The two of you
Cancer. You feel real when the room is safe. People see the care. They come to you when something hurts.
Sagittarius. You feel real when the horizon is still open. People see the range, and the person who makes a bigger story believable.
What wears it out
A cold room drains you. So does having to pretend you do not mind.
A small life with the door shut drains you. So does being managed for your own good.
Cancer feels it first and explains later and starts things. Sagittarius runs hot and wants it now and adapts quickly, and may not finish.
Nothing in the two signs locks on its own. Some days you understand each other. Some days you are solving different problems in the same room. Together, it shows up as the work of an ordinary day. The other way around, it shows up as sex and what they cannot take lightly.
This is the answer people want before anyone knows a birth time. Two real people have more than a sun sign. If it matters, cast both charts.