Christmas doesn't come around everyday and you won't always have an opportunity to say thank you, to the people you care about.  Personally, I think one should say thank you, I love you, I care and I'm sorry - whenever you think about it.  Life is so fleeting and before you know it - another year will have passed, another life will have extinguished and gone will be that opportunity you said, you'd get around to...  Leaving it until tomorrow will be too late - there is only now to say everything you want to say.