Hola Inma,

I'm struggling with this construction. I have been googling and found that saber and agradecido/a are commonly put together presumably meaning "to be grateful (for)" perhaps. 

Therefore I'm stuck on the use of sé, as this is the first person "I know" and that doesn't translate because the article is about giving advice  / using the imperative, but the speaker definitely says "se or sé." I thought that agradecerse was the verb leading me to write down "se agradecido" but I don't think you can use the pronominal in this way. So that may be another dead end!

Can you help me make sense of this please?

Saludos. John