It basically means "best of luck with everything that you are trying to accomplish." Endeavors are your attempts to accomplish something. For example, if you are trying to learn English, you are endeavoring to learn English. It can also be used as a noun, as with your sentence: You are on an endeavor to learn English.

加强语气，使句子变得更为恳切！

It means 'in whatever you do'. It makes the wishes more general.