You cannot look away. You also cannot turn them into you.
The two of you
Gemini. You feel real when the conversation is alive. People see the quick mind, and someone who can talk to anyone.
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
Being told to pick one thing and stay there drains you. Silence that means you should stop asking does too.
A small life with the door shut drains you. So does being managed for your own good.
Gemini needs to talk before it feels real and adapts quickly, and may not finish. Sagittarius runs hot and wants it now and adapts quickly, and may not finish.
Each of you is what the other is not. It holds when the difference stays interesting. It breaks when one of you starts correcting the other. Together, it shows up as the person across the table. The other way around, it shows up as the person across the table.
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.