1. Your texture doesn't just slightly change—it becomes a unmanageable mess.
Hair responds differently to bleach, but anytime you are opening up the cuticles of your strands to let chemicals oxidize the color that's in there, you can be sure whatever texture you once had will be no more. Most commonly, fine hair becomes rough, dry, and thicker.
What they don't tell you? Bleached hair can also become straight, curly, frizzy, or insanely brittle and the texture can continue to change the more you wash it. Since bleaching rips your cuticles open, those layers can continue to leak out whatever is left every time you wash. So even if your natural curls are there the day of your bleach, they might be gone tomorrow, no matter how much conditioning treatment you're using.
2. Purple shampoo is not optional (and taking a shower with the stuff becomes a scene from a meth lab).
If you have white-blonde hair, you need purple shampoo. Repeat: NEED IT. Your hair will turn yellow without it. On the flip side, when using purple shampoo, be incredibly careful and make sure it's completely rinsed out, because that crap stains towels, pillow cases, clothes, you name it, and can quickly turn hair lavender blue if any residue is left behind.
3. Bleach strips every last drop of moisture from your hair, so, you're now part of the "Newport Beach/Beverly Hills high maintenance" club.
Remember when you forced every last drop of pigment on your head to become completely colorless? Turning that straw mop into human hair within an hour is nothing short of a miracle. Tack at least an extra half an hour to your getting-ready routine; otherwise, get used to being that person who always shows up late.
4. Your makeup, and your wardrobe, are now useless.
Changing your hair color drastically alters your perceived complexion, and you might not match your wardrobe or any of your makeup. What was once a rosy and dewy complexion is now a washed-out puddle, and all your favorite lipstick color will suddenly clash with your face. On the bright side, black has never looked so chic.
5. Once you bleach, there is no going back.
Colorists will politely laugh in your face if you suggest dying your hair back to its natural color. The melanin is now banished from those golden Rapunzel locks. That color can never be fully added back. Bleaching keeps the cuticles on your strands wide open, so even when you do get close in color, each attempt at chocolate brown hair will wash down the drain the moment you step into the shower.
The only real way to get back to your natural color, is, obviously, growing it out. Or praying to the hair gods for faster growing hair. When in doubt, consult your colorist. Ask about lightening your hair with color instead of bleach.
Just offering a little of my experience and knowledge.