To be or not to be It's less a probe into grammatical validity than a personal preference in elements of style. Line 1 - Goes either way. Line 2 - I'd go with ' is ', it just reads better, gels better with modern writing biases. Line 3. It's essential to not panic --- Sounds more in poetic prose and eloquence of intellect. Either ways it's not degenerative in soundness of grammar per se.

The correct expression is “get enough sleep” and not “have enough sleep” then you say: Getting enough sleep is vital. Now because the sentence has two subjects: “getting enough sleep” and “taking regular breaks” so the verb to use is “are” so the verb you used is correct. The second sentence: we say “beneficial to you” instead of “for” so: Maintaining a schedule and adhering to constant training are beneficial to you. The last one is totally fine. Keep up the good work!

The correct expression is “get enough sleep” and not “have enough sleep” then you say: Getting enough sleep is vital. Now because the sentence has two subjects: “getting enough sleep” and “taking regular breaks” so the verb to use is “are” so the verb you used is correct. The second sentence: we say “beneficial to you” instead of “for” so: Maintaining a schedule and adhering to constant training are beneficial to you. The last one is totally fine. Keep up the good work!

For me all the options you mention work in English, sometimes 'is' works as a substitute for 'are' and vice versa - but not always, so I'd use 'are' after plurals as a general rule to begin with. And the last sentence works both ways too - in my opinion.