If you forget to take the contact lenses out, your eyes may get high possibility to get infection. The invisible bacterium will arise in your eyes to damage your eyes. You may get damage at the visual nerves at the retinal. You should better take the contact lenses out before you go to bed and remember not wear it for more than 8 hours a day.
Please remember to take off the contacts before go to the bed. If not, you will find it difficulty to take off the contacts in next morning, because the contacts and eye glued together, and it's easy to get hurt when you take them out. In addition, you may get blurry eyes if you forget it, your eyes are oxygen-deficient during the night, eyes are easy to be infected by bacteria. So you can't get a clear vision in next morning. And i think you'd better take some eye drops if you forget to take it out.
If you forget to take out your contact lens during night, irritation and redness will occur. It is bad for you to wear contact lenses all the time, even night. Actually, wearing contact lenses your eyes may be lack of oxygen and water. Then redness and irritation will happen.