It feels easy, like you already know how to be around each other. The risk is you stop choosing it.
The two of you
Aries. You feel real when something is starting. People see the one who goes first. The heat is obvious, and so is the courage.
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
Waiting drains you. So does a room that manages you instead of letting you move.
A small life with the door shut drains you. So does being managed for your own good.
Aries runs hot and wants it now and starts things. Sagittarius runs hot and wants it now and adapts quickly, and may not finish.
Wanting each other is not the hard part. Staying awake to each other is. Comfort can turn into taking the warmth for granted. Together, it shows up as the bigger plan, farther away. The other way around, it shows up as romance, play, and being admired.
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.