Beck has claimed that he is like lightning (fast and blinding).

Jade has claimed to be just like thunder (loud and frightening).

Jade is blinded by Beck and is so afraid that one day he will be the one to leave her and that she will not be able to catch up or hold on. She's afraid that he will be too fast, too fleeting for her to hold on to (lightning never strikes the same place twice). How long lightning lasts depends on the storm and she's afraid that soon he will end and never be back, because she is Jade West and sooner or later her luck will run out and Beck is like lightning, so once he leaves he'll be gone (because lightning is beautiful and fast and stunning and breathtaking and heartbreaking) for good.

(Beck's just afraid that he's going to burn out like a supernova)

Beck is deafened by Jade and is so worried that one day she is going to succeed in frightening him away (if only for a moment) and then she will be gone. He is worried that she'll scare herself away; that she'll let her doubts and fears roar through her head so she cannot hear anything else (not even him). He worries that she will be too loud with her plays and her songs, and someone will discover her and she will be gone. Thunder can last a very long time, but time is relative and Beck is afraid that his time with Jade is running out, because she is thunder and stronger than him (she can let go).

(Jade is just afraid that she will always be heard but never seen)

Jade loves Beck's beauty and Beck loves Jade's voice. Beck loves Jade's force and Jade love's Beck's speed. Jade loves that Beck is lightning and Beck loves that Jade is thunder (they belong together).

But they are scared (lightning and thunder are always associated with one another but never happen at the same time).