Have paid off / paid off

"My efforts have finally paid off."

"My efforts finally paid off."

I thought I already knew how to use present perfect tense and past tense, but all of a sudden, I could not explain when I should use the first sentence and what the difference is between them. Could you help me out and I am really sorry for taking your time too often. But I would like to say, Merry Christmas!! Ho Ho Ho...:-)

The first suggests a more recent happening. You made some efforts and they have just recently paid off, fairly recently before saying the sentence.
The second suggests the past. You made some efforts at some point in the past, and at some later point in the past, they paid off.

I started a diet in January 2012. This morning, I weighed myself and I have lost 16 kilos. My efforts have paid off!!!

I started a diet in January 2011. By June 2012, I had lost 16 kilos. My efforts paid off but unfortunately I've gained 10 kilos back since then.