@ CHIRADEEP,
I was working throughout my study tenuer. For Costing I referred only ICAI study material - throughly - and compilation only.
I was starting with how many effective hours I would have for study and then dividing them into the subjects - more weightage to costing and remaining in balanced way in other three subjects.
For my last attempt I had managed to get 3 months without pay leave from the company. Earlier it was just 8-15 days leave. I attended DT & ISCA Classes at pune, IDT revision batch at Pune.
I was studying for minimum 12 hrs a day and then at night checking the company mails and replying to them - both were going side by side.
keep yourself healty and tension free during your study time - keep yourself away from negativity - read short stories regarding positiveness frequently - and remember only one thing that at any cost you have to achieve your goal.