If you compose music about relationships that you've had,you've been, or you are in right now..?

how would you describe…say.. to write music journal? and what key would you start with…?practical C major or melancoly D minor or cheerful Eb major…??? As for me, it is quite dynamic(lots of pp's and ff's) and has lots of characteristics; cheerful, cheeky, elegant, and at times– furious and passionate…so i would start with E [...]