Supporting Spouse in New Business Venture

My husband is a big dreamer. He is that guy who doesnt want to work for anyone and be his own boss. So he started a business with some high school buddies and he is ready to just up and quit his steady job with benefits to drive Uber and work solely on his business. Im trying to be supportive but Im so afraid I keep saying yes to things when really I feel he should pump the breaks. What if it all works out and we are financially stable? But what if they take on too much and cant handle the workload? I just am kinda stuck with my thoughts to myself because I dont want to crush his dreams