The meaning of "perspective" here

To lose perspective is an expression in which perspective means:

a sensible way of judging how good, bad, important etc something is in comparison with other things

• lose perspective: He has lost all perspective in the rush to get what he wants. (macmillan)

Longman is a bit more precise, defining perspective as:

a sensible way of judging and comparing situations so that you do not imagine that something is more serious than it really is

• I think Viv’s lost all sense of perspective.

So your sentence

Looking up at the sky too much makes you lose perspective

probably means that one must be careful not to focus too much on ideals or things that are out of reach, thus losing grip on reality.

^{NOTE: This seems to be the title of an instrumental track by Crepehanger.}

My interpretation is that the sky is so grandiose that comparisons to most things is close to impossible, probably suggesting that focusing on the sky too much makes everyday objects appear disproportionately insignificant. A very crude example might be that somebody becomes very dismissive simply because ”space is big”.

I can’t really disprove a reference to physical sciences here but it looks obviously proverbial. While not same exact word, Merriam-Webster supports this interpretation in their entry for stargazing .

There can be several interpretations for this sentence...First of all, 'sky' may be a metaphor for some authoritative power or a 'God'...which means we should not derive every meaning from god or else we won't be able to explore anything else and our intelligence will be cluttered.............2nd possible meaning is that if you focus on one thing always then you can lose the perspectives of other things...3rd interpretation can be....if you imbibe the vast angle of sky all other small perspectives will be included or dissolved into it.......................But to be sure which one is correct we must look the context of other sentences before or after the sentence posted in the question. I hope this helps.