Why it is imp to Select Stocks for Investment with Diligence?

In Last 3 Years 

1) Largest Paint Company: Asian Paints: -29%

2) Second Largest IT: Infosys: +7%

3) Largest NBFC: Bajaj Finance: 0%

4) Second Largest Cement: Shree Cem: +5%

5) Largest FMCG: HUL: +5%

6) Largest Media: Zee Ent: - 62%

7) Second Largest Paint: Berger: -29%

8) Second Largest Insurance: HDFC Life: -5%

9) Largest Pizza Comp: Jubilant Foods: -5%

10) Largest PSU Steel: SAIL: +6%