But panic not .. it doesn't have to be totally German ...any bits you can drop in will do for now.
Plus, it doesn't matter if you get it a bit wrong.
That's important ... "fear of getting it wrong" is a huge barrier for many learners.
Plus ... diaries tend to use a limited range of expressions ... also a big help.
This means you can compile a sort of " Diary words and phrases" list.
You may think that's cheating .. but repetition is a huge boost to learning a language.
Repetition repetition repetition repetition repetition repetition repetition repetition...
Here's some examples of " diary words and phrases" from my very own list ...
wie eh und je .... as always
meinen .. to think
warscheinlich .... probably, likely
etwa .... about, roughly
bedeuten ... to mean, to signify
zufällig .... luckily, by chance
beobachten ... to watch, to observe
vorkommen .. to happen, to occur
das Ding .. the thing
sozusagen ... so to speak
nach und nach ... gradually
trüb = cloudy, dull
elend ... miserable
gestern .. yesterday
das Pech ... bad luck
der Pechvogel ... unlucky person
überascht ..surprised
immerhin ... after all
traurig ... sad, dismal
zunächst ... first of all
passend ... suitable
zumindest ... at least
manche ... many
der Besuch ... visit
bis ... up to, till
sonst ... else/otherwise/formerly
ruhen .. to rest
das Geheimnis ... secret
diesmal ... this time
anschauen ... to look at
Obviously your list might be very different ... it depends on what you do all day, what your interests are ... but writing a diary means you are going to use this stuff every day, and that way you'll learn it, expand it ... it has to be Terrific For your German.
Here's Glasperlenspiel mit " Ich bin Ich" ....