Pero no te quedes ahí dándole vueltas a la cabeza, que tanto pensar no es bueno.
[Caption 29, De consumidor a persona > Short Film > Part 1]
Que most often means "that." Slap an accent on the final e and we have qué, used to ask the question "what?" -- add por before qué and you have ¿por qué?, which asks the question "why?" ¿Por qué? is two words, but if we push the two together, without the accent on the e, we have porque, which is one word, and it means "because."
You may just know all that. What you might not have known is that que can also mean "because," or "as," and that's the meaning it takes in the line above:
"But don't stay there making your head spin, because [or "as"] thinking so much is not good."
No comas más, que no es bueno antes de ir a la cama.
"Don't eat more, as it's not good before going to bed."
Obedéceme, que si no lo haces, te vas a arrepentir.
"Obey me, because if you don't, you are going to regret it."
No corras, que el piso está mojado.
"Don't run, because the floor is wet."