Босиком (bosikom) literally means "barefoot". It’s a simple word that JONY uses to create one of the song's most powerful and heart-wrenching images.
He sings, "Я босиком по стёклам бегал так упрямо" (I ran barefoot on glass so stubbornly). This is a vivid metaphor for enduring immense emotional pain, perfectly capturing the feeling of desperately and stubbornly holding onto a relationship that is only hurting you.
Picture this: it is six in the morning, and while normal people are sleeping, JONY is sitting alone by the fire burning his ex's photo. The chorus sets the whole mood with «В камине в шесть утра / Фотография твоя / Горят воспоминания» [In the fireplace at six in the morning / Your photograph / Memories of you are burning]. There is zero chill here. He stares at a «разбитая душа» [broken soul] and writes off all her promises as complete «пустота» [emptiness]. It is dramatic, dramatic pop at its best, treating a nasty breakup like a full-blown physical scene with ashes flying everywhere.
He doesn't sugarcoat how exhausting the relationship was, either. He admits he was stubbornly hurting himself just to make it work, dropping the dramatic metaphor: «Я босиком по стёклам бегал так упрямо» [I ran barefoot on broken glass so stubbornly]. Literally running barefoot on broken glass! Russian uses «стёкла» (plural for glass shards) here to spell out how self-destructive he was being. Even though he used to wish on shooting stars («звёзды мирно падали» [stars were falling peacefully]) just to keep her, he hits his limit. He bluntly tells her «Уходи, за собой закрой» [Leave, close (the door) behind yourself], deciding that suffering over an ex who chose to slip away is no longer worth losing sleep at 6:00 AM.