Most budgets fail because they're aspirational, not realistic. Writing down that you'll spend $200 a month on groceries when you've been spending $450 isn't a budget. It's a wish list.
Start with what you actually spend. Pull your last three months of bank and credit card statements. Categorize everything. Don't judge it yet, just document it. You need the real numbers before you can make a plan that works. Most people are surprised by at least one category (subscriptions and dining out are the usual culprits).
Now build the budget around your actual life, not a fantasy version of it. Use the 50/30/20 framework as a starting point: 50% of take-home pay on needs (housing, utilities, minimum debt payments, groceries, insurance), 30% on wants, and 20% on extra debt payoff and savings. But adjust those percentages to your reality. If housing alone takes 40% of your income, the other categories have to flex.
The debt payoff piece is the 20% (or whatever you can manage). This is the money above your minimum payments that actually makes your balances shrink. Even $100 extra per month on a $10,000 credit card at 24% cuts your payoff time from 30+ years to about 14 months and saves you thousands in interest.
Build in a buffer for irregular expenses. Car repairs, medical copays, birthday gifts. These aren't surprises. They happen every year. Estimate $100 to $200 per month for the stuff you can't predict, and put it in a separate line item. If you don't use it, roll it into debt payoff at the end of the month.
Use a tool that works for you. Some people like spreadsheets. Others use apps like YNAB, Mint, or EveryDollar. Some prefer a simple notebook. The format doesn't matter. What matters is checking it weekly (not monthly, weekly) so you can course-correct before small overspending becomes a blown budget.
One more thing: a budget that doesn't include any fun will fail. Budget something for entertainment, coffee, or whatever keeps you sane. Deprivation budgets last about six weeks before people give up entirely.