There comes a point during a bout of tickling when a lee goes from being somewhat in control of their reactions to losing it completely. Where the "tickle panic" sets in. It doesn't happen with everyone, but it's common. If you stop frequently enough, they never cross the threshold, keeping the session very tame, which is lovely. If you get them past it, they let go and lean into that lack of control, which is lovely (however, I don't like to push to safeword unless the Lee asks for it).
That bit in the middle, the "tickle panic" is a key moment for me in my sessions. Some lers let lees ride that alone, some will humiliate or tease a lee through it. I'm not saying either of these are wrong. Some lee/ler combos want intense. But for me, I do something different.
That moment of panic is sometimes laced with doubts and anxiety. You can see the lee fighting to maintain some sort of control. This fight can be to ground themselves so they can take it for longer. But it can also be because they're anxious about their reactions. They worry about how they look and sound when they're laughing hard, whether they're squirming too much, their appearance, their volume... so many factors. If you make them give up that fight, they'll forget about those things. But chances are they'll remember them on the way back down, and may overthink them.
I give them permission to give up. When I see that "tickle panic" setting in, I speak. If I'm at their upperbody, I go close to their ear, so they feel my presence more. I keep tickling. And I guide. And reassure. And praise them out the other side. It sounds something like this:
"I know darling, I've got you. It's okay, you're doing beautifully. Let those reactions out, you're safe. Come on, laugh for me, just let it happen. Let it tickle. You look so pretty squirming for me like this, you're just adorable. Awww so ticklish, aren't you, there we go! There's that laugh, you're doing so well sweetheart." Then resume gentle teasing accordingly
It squashes all of that anxiety about being "too much" and lets your lee know that you want to see their full authentic selves. And post session, I remind them of all that again. And as many times as they need it following the session. I don't give those anxious thoughts a chance to take hold, they're reminded how well they did, how adorable they looked, and how precious every reaction was. Because if my lees don't feel safe and comfortable with me, I haven't done my job at all