Tool bar Issue

using shorcut on keyboard for working with another tool it dosen't get active, i have to press for more than four times after that the required tool is active,

for exampe suppose i am working with clone stamp tool, and in between i want lasso tool to use i press L the shourtcut key on keyboard, but the tool dosen't get working, i have to press the shortcut key again & again after that it active to use, or i have to choose from the tool bar manually.

Please help me with this problem