Looking for a word to describe the desires of your heart, in other words, what you are constantly thinking, or what worries you. Usually things you would only confide with very close friends.
Love captures one end of true desire:
3 [COUNT NOUN]
A person or thing that one loves:
As the quote from Miley Cyrus confirms:
Music is the love of my life. It’s a total escape from reality. Music transports you to another place, someplace unexpected and meaningful.
Miles to Go, retrieved from goodreads.com
The etymology shows that love is rooted in desire:
Old English lufu "love, affection, friendliness,"
from Proto-Germanic *lubo
(cognates: Old High German liubi "joy," German Liebe "love;" Old Norse, Old Frisian, Dutch lof; German Lob "praise;" Old Saxon liof, Old Frisian liaf, Dutch lief, Old High German liob, German lieb, Gothic liufs "dear, beloved").
The Germanic words are from PIE leubh- "to care, desire, love" (cognates: Latin lubet, later libet "pleases;" Sanskrit lubhyati "desires;" Old Church Slavonic l'ubu "dear, beloved;" Lithuanian liaupse "song of praise").
If you don't want people to know about these desires (especially if they worry you), that might well be because you're ashamed of and tormented by them. In which case they're your...
a persistently tormenting person, force, or passion
a person, habit, obsession, etc., thought of as evil, cruel, or persistently tormenting
For an adjective to use with ‘desires,’ I’d probably say “innermost desires,” but that’s still two words.
Our innermost desires often help us discover our “raison d’être” and develop a “sense of purpose” (all still multi-words), which in turn helps us determine our “motivation” which is sometimes kept secret from everyone, even ourselves.
One adjective that can describe the "desires of your heart" is bona fide. Your bona fide intentions or loves are those which are true and authentic.
With respect to intimate thoughts or personal secrets that one would talk about only with a trusted friend, I think the term confidence may fit:
that which is confided; a secret: a friend does not betray confidences. (AHD)
something confided or entrusted; secret