Hence a ship is said to be tight, when her planks are so compact and solid as to prevent the entrance of the water in which she is immersed: and a cask is called tight, when the staves are so close that none of the liquid contained therein can issue through or between them.
If you're playing within your capability, what's the point? If you're not pushing your own technique to its own limits with the risk that it might just crumble at any moment, then you're not really doing your job.

