Most targets get more difficult to attack as the match goes on – the back is the exception to the rule: I'm sure you have all had the experience of trying to attack a submission hold towards the end of a match and found out the hard way that the inevitable sweat and overall makes it very difficult to and finish many of the major submissions. Most and become more difficult as sweat and slipperiness increase. Interestingly however, getting to an opponents back is barely affected by increases in slipperiness and arguably may even be EASIER. Many transitions to the back are helped by increased slipperiness rather than hindered. Sliding your arm into position also becomes easier with less friction. Holding the back for extended periods of time can be a little more difficult, but nothing that wrist control, good head position and a body triangle can't take care of. Next time you submissions are failing in slippery conditions – focus on transitions to the back – they make your easier rather than harder.