When running cold it is important to minimize your losses. The best way of doing so is to set a magic number and when you lost that, you stop no matter what. Many players do this to prevent the bad days from beeing worse than they have to be. Phil Ivey for example had a stop-loss of only one buy when playing online. I think a good number is somewhere between 3-5 buy ins when I play 4 -6 tables medium stakes. Of course the number depends on what stakes and the number of tables you are playing.
Of course there are situations when you should not stop even tho you’ve reched your stop-loss. An example beeing if there is an extremely bad player at the table. Of course it is up to you to figure out when it would be ok to bend the rules a bit. The most important thing when you play is that you are playing your A-game

Great.TY.You helped me well.
Glad I could help =) I’ll try to write something about head-ups play as requested asap=)