I wonder whether there are any idiom(s) meaning "While you know that your ultimate goal is impossible to achieve completely, you should try your best to at least get a glimpse of it because it's enormously valuable".
The nearest things I can imagine are "Getting a glimpse of your goal is better than nothing" and "Half a loaf is better than None".
Best Answer
Shoot for the moon - even if you miss, you'll land among the stars.
This phrase suggests that even a very difficult task can be worth undertaking, as even failure may bring some benefit. The ultimate goal might not be achievable, but trying to achieve it is still worthwhile.