Thanks for this question, Piotr! I like to think we can never be “too compassionate” for ourselves. The trick is to be able to tell the difference between compassion and leniency in your personal experience.
I think this is one of those questions that each person has to answer for themselves. To me, I learned to recognize how both of them feel in my experience, and this is honestly the only way for me to tell them apart. So I’m afraid I don’t have a good answer to your question!
In my experience, it’s been the matter of trial and error before I started understanding what is what (although I can still go wrong). I wrote more about this here:
Are You Slacking, Or Just Being Hard On Yourself?
When personal growth becomes a form of self-aggression
All the best and I hope you can find your balance!