Sasha, your sentence is mostly fine, just a few adjustments:
When you ARE (you’re) sleep deprived and SIMPLY (use “simply” instead of “just”) exhausted after A (there should be an indefinite article before “week” because you’re talking about any hard week, not a particular one) hard week, but (no comma after “but”) STILL have AN (don’t forget about articles before nouns) overwhelming feeling of happiness and love BECAUSE (use “cause” in your speech as less as possible, it’s slang and it’s not good English) it's holidays (1 “l” in “holidays”) next week.

Holy Moly, thank you :)

Anytime :)

Oh, and it’s also “sleep-deprived” (with a hyphen), because it’s an adjective.