"El mundo es un pañuelo":: you say this for example when you meet a friend of you, in a place where you never thought meet him or her.
"A palabras necias, oidos sordos", you use this sentence when someone is insulting you and you do not want to argue with him or her.
"Agua que no has de beber, déjala correr", you say this sentence, when you must not get into a problem of a person.
"No por mucho madrugar, amanece mas temprano", you say that to someone who lives its life so much quickly.
"En casa de herrero, cuchillo de palo", you say that, because you know that sometimes things do not happen as you hope or as they should must be.For example, there was a young man, who was a car mechanic and he had a car and he kept it carelessly --you can not understand it, if you do not think that when he finish his work, he is so tired and he does not feel like fixing his car--.
just in case you need clarification of certain words, in that sentence "En casa de herrero......", I am going to tell you the meaning of themThe.first one: Herrero (it is a man who works with iron).
The second one: Palo (it is a piece of wood, more large than width).
"Quien siembra vientos, recoge tempestades", this sentence means that when you makes bad things in your life, Life gives you back another bad things.And, also, if you make bad things against someone, you will not help by that someone.
Best regards,
Luis