Here is a quote which I received in my email and have never seen. If anyone knows its origins, I will gladly give that person(s) credit:
"El pasado te podrá servir como trampolín, nunca como sofá."
Anónimo (Personaje desconocido)
My translation is:
"The past can serve as a trampoline, never as a sofa."
Anonimous (Unknown author)
The source was the 'citadeldia' feature of this site. Their list of enlaces[links] is helpful.