The feeling is uneven. It lasts if you keep adjusting, not if you wait to match.
The two of you
Leo. You feel real when you are actually seen. People see the warmth, and the person the room turns toward.
Pisces. You feel real when you do not have to harden yet. People see the softness, and someone who understands before the explanation.
What wears it out
Being ignored drains you. Polite affection that never becomes admiration does too.
A demand to be definite before you are ready drains you. So does a hard room with nowhere to retreat.
Leo runs hot and wants it now and does not like to be moved once settled. Pisces feels it first and explains later 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 sex and what they cannot take lightly. The other way around, it shows up as the work of an ordinary day.
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.