Why must we do Pranayam/Sadhna everyday?
Do all of you buy insurance for your house, your car, your life even! You compare several policies to pick the Best one and gladly sign up to make regular payments month after month... to insure/protect yourselves in case something bad happens. After all it is what all sensible people do. You know that you cannot buy insurance after a crisis has happened!
The same way one must do Sadhna/Spiritual practices every day. Your daily Sadhna is small investment not only keeps you mentally and physically healthy on a daily basis but also acts as an insurance.
Most people think they are not missing anything if they don't do their practice everyday. They feel everything is going smoothly in their life.. so why bother putting this effort.
But remember when you are in a crisis situation, you will want to do everything in the world to solve it I.e. running to the doctor, a priest, a police, a lawyer etc. But that time, it is your Sadhna that will act as your insurance. It will shield you, it will help you take the right decision and protect you from extremeties.
Hence it is must be done everyday, when everything is running smoothly in your life, so it can act as your insurance during difficult times. @SriSri