polish this "It is very hard to build things that *lasts*, build sth that lasts is my new goal"

"It is very challenging to create things that endure. Building something that lasts is my new goal."

"It is very challenging to create things that endure."

"It is very challenging to create things that last."

Your sentence is clear, but if you're looking to polish it slightly, you could say:

"It is quite difficult to build things that last."

Your original sentence, "It is very hard to build things that last," is clear and grammatically correct. The only minor aspect that could be considered is the choice of vocabulary. For example, "hard" and "very" are perfectly fine, but using synonyms like "difficult" or "challenging" and "quite" or "extremely" might convey a slightly different nuance or tone. However, these changes are more about style than correctness.