Just realized how many people I know are walking into retirement with some pretty dangerous assumptions about money. Like, they think Social Security alone will keep them comfortable, or that Medicare magically covers everything at 65. Spoiler alert: neither is true, and these assumptions could seriously mess up your golden years.

Let me break down the three biggest ones I see people make:

First, the Social Security trap. A lot of folks assume those checks will cover their bills once they retire. But here's the thing—Social Security typically replaces about 40% of what you were earning before. Unless you're cool with a 60% lifestyle cut, you need other income sources. That's where your retirement savings come in. If you haven't been aggressive enough with your 401k or IRA, now's the time to look at your spending and see where you can trim. Even small bumps to your savings rate compound over time.

Second assumption that kills people: thinking Medicare is free healthcare at 65. Nope. Part B has monthly premiums, plenty of plans charge extra, and then you've got deductibles, copays, coinsurance piling on top. Plus Medicare doesn't even cover dental or eye care. People get blindsided by this constantly. If you can, max out a health savings account while you're still working—it's basically a dedicated fund for future medical costs.

Third one might surprise you: assuming you should dump all your stocks once you start living off your nest egg. Yeah, stocks are risky, but completely avoiding them is actually a bad move. A lot of retirees do a 50/50 split between stocks and bonds. You could even lean heavier into stocks if you keep a couple years of living expenses in cash as a buffer. The key is finding the right balance.

The real lesson here? Don't let bad assumptions dictate your retirement. Get realistic about Social Security and Medicare costs, work with someone who knows their stuff on portfolio strategy, and make sure you're positioned to actually enjoy retirement without constantly stressing about money.