Ganas

The noun ganas means something like deseo, desire. Let's look at some common expressions with ganas.

Tengo ganas

You can use tener ganas to express your interest — or lack of interest — in doing something. No tengo ganas. I don't feel like it. I'm not up for it. I'm just not in the mood. Ya tengo ganas de estar ahí. I really want to be there, I can't wait.

Note that the complement does not have to be a verb: tengo ganas de tacos = I feel like tacos. I'm in the mood for having tacos. Tengo ganas de ti is ambiguous, ranging from a simple expression of affection to a sexual come-on.

Se me da la gana

Se me da la gana expresses the idea of feeling like doing something.

• Cuando se me dé la gana. When I feel like it. When I feel like doing that.
• Yo hago lo que se me da mi regalada gana. I do exactly what I want, live my life on my own terms. As a variation, it is possible here to substitute la for mi: la regalada gana.
• Haz lo que se te dé la puta/chingada gana. Do whatever the fuck you want.

Note the grammar of this expression: It begins with se, followed by a pronoun referring to the involved person, for example, me, te, le, etc. I've also heard this with pegar: cuando se me pegue la gana, when the mood strikes me.

Me muero de ganas

• Me muero de ganas de verlo. I'm dying to see him.
• Me muero de estar contigo. I can't wait for us to be together.

The translation into English, I'm dying to, is direct here. Just remember that we need the pronominal particle: me, te, se, etc.

Ganas no me faltan

Here is a handy way of prefacing the rejection of an invitation.

• Ganas no me faltan. Believe me, it's not that I don't want to. It's not for lack of interest on my part. I would love to. It's just that ...

Quedarse con las ganas

Quedarse con las ganas conveys the idea of not having your needs fulfilled.

• Que se quede con las ganas. Let him suffer a bit. Don't give him what he wants.

There's a related construction with dejar: ¿Me vas a dejar con las ganas? You're just going to leave me here like this (with me wanting more)? I tend to associate this with blue balls, sexual frustration, but maybe that's just me.

Echar ganas

The basic idea of echar ganas is make an effort.

• Pero te juro que voy a echar muchas ganas. But I promise you that I will give it my best.
• ¡Échale (muchas) ganas! Go for it! You can do it! Give it your best shot! I've heard this shouted at runners to encourage them during a road race.
• Por más ganas que le eches. No matter how hard you may try.

You can think of le in these last two examples as referring to the situation at hand.