How risky is it to hold a lot of one stock, like my employer's?

Single-stock concentration is one of the biggest avoidable risks investors carry, especially with employer stock from RSUs or ESPP. A diversified index fund spreads your money across thousands of companies; a single stock can drop 50% or go to zero on company-specific news — and if it's your employer, you could lose your job and your savings at once. A common guideline is keeping any one stock under 10% of your investable assets. If RSUs have pushed you well past that, the cleanest fix is selling vested shares as they unlock and reinvesting in broad index funds — vesting-day sales usually trigger little or no extra tax since shares are taxed as income at vesting. Diversifying isn't disloyalty to your company; it's protecting your future from a single point of failure. wealthserene.com/tools/rsu-espp-calculator can help you plan the sell-down.