How many years I needed to learn how to search my own posts. 
It's too easy. 
Type into the #search:
from:@username searchwords
or
from:me searchwords
It also works (for yourself) if you have disabled being in the public search.
Thanks @MythingPerson for the 2nd, much easier method!
@NatureMC You can also say
from:me searchwords
instead of typing your full username, which was super clever of them to implement. 
@MythingPerson Oh thank you! I learnt again something new. 
@MythingPerson @NatureMC hard to look for stuff from @Me on your instance though ;-)
@oblomov Well, that's an empty account.
And if you want to search me: I didn't opt in to public search. Has nothing to to with the instance but with GDPR: You have to opt in if your content should be searchable for the public.
@MythingPerson @Me@sociale.network
@NatureMC @username @MythingPerson this is indeed a handy feature, but it has not been implemented in mastodon for *that* long. I think in version 4.2 somewhere. So no need to feel bad about not knowing.
@NatureMC just saw your edit about from:me, deleted my reply.