Rabbi Yisrael Lipkin of Salant
It is forbidden to worry, except about worrying.
From Tenuas HaMussar (The Mussar Movement)
Modern Uberdox
“I write not because I have the strength to write, but because I do not have the strength to remain silent.” -Rav Avraham Yitzchok Kook zt’l
Is this available in English?
Yes, as THE MUSSAR MOVEMENT by R Dov Katz and translated by Rabbi Leonard Oschry.
The translation has a vol 1 and vol 2. Part 1 is mostly about R Yosef Zundel M’Salant, the rebbe of R Yisrael. It does contain a biography also of R Yisrael.
Part 2 is exclusively about R Yisrael. His techniques, struggles, successes, an extensive list of quotes and excellent footnotes that reference Ohr Yisrael (a collection on his letters/writings compiled by his talmud, R Naphtali Blazer).
I’d suggest Google Shopping and also online searches for used books to find a copy.