This is the problem which every new trader has to face. What % to reinvest depends on whether one is in capital building stage or capital preservation stage. In capital building stage of a new trader his capital is small, household expenses and housing loan installments take away major chunk of the profits leaving very little for capital formation. This happens with every new trader. It happened with me too and the capital formation is slow. But one should invest back 50 % of the profits in capital formation stage. Once capital acquires a critical mass, then the profits increase rapidly and our expenses dont increase in the same proportion and then the capital formation process becomes faster.
In capital preservation stage all financial needs, present and future , are met and the trader trades not for making more money but he trades because he enjoys it and that gives him occupation and income apart from fulfilling his passion. In this stage money ,though important, assumes lower priority. In that case he may take out all 100 % of profits and invest it elsewhere.
I too used to have same questions when I was in capital formation stage, I was into trading full time, no other income source,no inheritance in terms of money, and household expenses and HDFC housing loan installments to be met from trading income....but after a few years the capital grows in exponential proportion....so just concentrate on trading well and making consistant profits...all other things will fall in place .
Smart_trade