How do I break things off with my boyfriend of four months without mentioning his faults to him?

I'm learning that My boyfriend (30) I'm 28, has a long history of work instability. He just quit his job of two years without a backup plan. He also tends to be impulsive with his decisions. I'm very concerned that he won't be a good future provider/husband. I know that he knows he's fully aware of his situation and issues. Is breaking things off already a good reason? I can't see this man changing anytime soon. I'm having a hard time breaking things off because I always have these "what ifs" questions in my mind. How do I end things without bringing up his big flaw? considering that this man is delusional about how this is a really big issue and yet he continuously fantasizes having a home and children with me.
How do I break things off with my boyfriend of four months without mentioning his faults to him?
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