Psql is a fully-fledged CLI client for Postgres, but most people are unaware of its many advanced features.
~/.psqlrc can be edited to persist any behavior or configuration settings you want between psql sessions. It behaves just like ~/.bashrc or ~/.vimrc, sourced at psql launch. See More out of psql for some interesting configurations.
If you have a long query to write and rewrite, you can use \e to edit your query in an editor.
Use \watch at the end of a query in order to automatically re-run the query every few seconds - great for monitoring while making changes elsewhere in your application architecture.