Tobacco is associated with tamas.
It is quite true that the physical exercise is very necessary to keep off tamas. I am glad you have begun it and I trust you will keep it up.
Physical tamas in its roots can be removed only by the descent and the transformation, but physical exercise and regular activity of the body can always prevent a tamasic condition from prevailing in the body.
The weakness of the body has to be cured, not disregarded. It can only be cured by bringing in strength from above, not by merely forcing the body.
The first rule is — there must be sufficient sleep and rest, not in excess but not too little. The body must be trained to work, but not strained beyond its utmost capacity.
To become conscious of what is to be changed in the nature is the first step towards changing it. But one must observe these things without being despondent or thinking "it is hopeless" or "I cannot change". You do right to be confident that the change will come. For nothing is impossible in the nature if the psychic being is awake and leading you with the Mother's consciousness and force behind it and working in you. This is now happening. Be sure that all will be done.