Those who have given themselves totally to me, even for a single moment, they do not have to worry about their liberation. Liberation is assured. To live gracefully or not, that is not assured. That is something that you have to earn. There is no other way.
The reason why sadhana is done is that life is not 100% in your hands. Many people may not run their full prarabdha, either because of injury, accident, disease or for any reason. Most people die in hospitals today because they are not running their full prarabdha. How many people die every day, without any ill health, just out of old age? It is a small percentage.
Sadhana is done so that you create a certain sense of awareness, and you are hastening the process of the dissolution of karma so that your prarabdha gets finished faster and faster. If you dissolve some aspects of your prarabdha – generally you are working towards the mental and emotional dimensions of your prarabdha – you can live in a blessed state for a longer period of your life. If you dissolve them, your physical prarabdha is still there, so you continue to live, but without the struggles of the mind and the emotions. That is a blessed state. When physical prarabdha is over, the body will drop itself. The possibility of liberation is so much higher.