Computers and cellphones exist to assist us in being awesome at the task we choose. A computer can't replace you and it can't be better than you.
Yes, computers can add faster than you can, but adding probably wasn't your core task anyway. You were trying to use your insight and creativity to perform and important task. Maybe that's solving physics problems, or entertaining your friend with a text.
It can be easy to forget that in our relationship with electronics we have the upper hand. So please don't sell yourself short. You are the one with the ideas, no matter how simple or complex.