How do I break these habits?

[SCalScoreKeeper]

Hey All,
Worked a varsity match tonight as a linesman that went 4 sets and I need some advice on how to break a couple of bad habits-

A.When I have a ball that is barely going to catch the endline I have a tendancy to drift off the line and follow it down instead of staying straight up but turning and following it down.

B.When I have a swing from the back row I have a tendancy to leave the net and get into position to call the line leaving myself in a vulnerable position to miss a touch call.In fact I had such a play tonight.I know I need to stay with the ball longer and then get into a position to call the line-How do I do that?

Today I did a better job of getting behind the server instead of going endline extended although I would start at endline extended,catch myself,then move back to the right spot.

One of our area evaluators was there and told me about these habits but he had to go home and submit his report.Another question-this time regarding libero jersey compliance: If the home team's uniform is black would you consider a dark purple uniform to be of acceptable contrast?

Thanks for the responses!