私は、彼がいなくてこの上なく寂しい。

I; me; private affairs; personal matter; secrecy; selfishness

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

he; him; his; boyfriend

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

to be (of animate objects); to exist; to stay; (after the -te form of a verb) verb indicating continuing action or state (i.e. to be ..ing, to have been ..ing)

this (something or someone close to the speaker (including the speaker), or ideas expressed by the speaker)

above; up; over; elder (e.g. daughter); top; summit; surface; on; before; previous; superiority; one's superior (i.e. one's elder); on top of that; besides; what's more; upon (further inspection, etc.); based on (and occurring after); matters concerning...; as concerns ...; since (i.e. "for that reason"); suffix indicating higher social standing; place of one's superior (i.e. the throne); emperor; sovereign; shogun; daimyo; noblewoman (esp. the wife of a nobleman)

nonexistent; not being (there); unpossessed; unowned; not had; unique; indicates negation, inexperience, unnecessariness or impossibility; not ...; to not be...; to have not ...

lonely; lonesome; solitary; desolate