Prayer is one thing. Prayer on your knees is another. It means full surrender, it means true worship, it shows God you're serious.
This may sound crazy, but I feel taller when I'm on my knees in prayer.
I've hit my knees in prayer every single day (multiple times per day) since September 29th, 2014, and I've been free from my alcoholism and drug addiction since that day. Coincidence? Definitely not.
Show God you're serious, and He will move your mountains.