Dear Anshika,
It is good to note your enthusiasm to learn and gain knowledge. Coming to your query, I do agree that investing when the market is low is of utmost benefit. In fact, everyone would agree to that.
The problem is, how do you decide whether this is the bottom of the market ?? In 2002-03, the Sens*x had hit a bottom of 2900, whereas in 2008-09 when the market was falling people were waiting for the bottom of 4000-5000 and the market reversed from 8000 levels itself.
Over period, you will observe that we are moving towards higher tops and higher bottoms. So its really difficult to catch the bottom everytime. Also, its not necessary that you have surplus cash exactly when the market hits a bottom. These are my Personal views. Could be right or wrong.
You can get in touch with me for any advice you need. You can send me a PM or a mail with your query.