Treat it as such
“Ninety miles is only half of a hundred-mile journey” (行百里者半九十 – Xíng bǎi lǐ zhě bàn jiǔ shí).
– Chinese proverb
This alone says enough. Don’t allow yourself to end prematurely when the end is in sight. Don’t let your foot off the accelerator just yet. There’s still work to do. Make it 100% before you even think of celebrating.
When I’m swimming, this is the final 200m of a long set. It sometimes truly does feel like you are only halfway. You’re not, and you can let your adrenaline keep you ticking, but you shouldn’t rely on that at the same time either. Keep the 90% is halfway concept at the back of your mind.