Brujeria? or How much power does my abuelita actually wield?

Amy here.

I have a burning question that I thought maybe some of mom's Cuban blog readers could answer.

Here's the story:

My Cuban Abuela curses and blesses me.

The blessings go something like this: 
"Algun dia tu nieta hara lo mismo por ti." ("One day your own granddaughter will do the same for you.") 

That sounds like a blessing. . . right?  She's in effect saying that I will one day have grandchildren of my own.  It makes me happy.

In the next breath (just after I beat her at cards the other night):  And I'll just paraphrase here . . .
"I didn't want you to win because you know what they say about 'lucky in cards, unlucky in love' and I'd hate to see you end up an old maid. How old are you again? Maybe you should just start buying your cats now." 
That sounds a little curse-like to me.

My question:
How much power do these Cuban-abuelita-curses/blessings have?

Just wondering if I have to go to church and light some candles or something. . .