hand-to-mouth existence; scraping by financially
Describes a precarious financial situation where one lives from day to day with barely enough to get by. Often used in phrases like その日暮らしの生活.
He lives a hand-to-mouth existence.
Since losing my job, I've been barely scraping by day after day.
living day by day without a plan; taking life as it comes
Focuses on a lifestyle of not making long-term plans, simply living each day as it comes. Can carry a nuance of carefreeness or lack of foresight depending on context.
She lives day by day and doesn't think much about the future.
When I was young, I lived without a plan and never saved money.