There are a lot of people here making it harder than it has to be.
There are a few people that I think are over dramatising things but over all there is some good advise here.
I think my main habits are:
1. I assume that any other pilot I come into contact with in the air has no idea what they are doing (no offence meant to anyone). This may sound a bit egotistical but it has helped me in a lot of situations.
2. There is always something to do, even if you are sitting there bored (as I am most of the time) I run through "What Ifs"... What if I lose an engine, What if I have to divert, what if I have to get on the ground ASAP.
3. Always have a couple of options available for different situations.
But I think the main thing is (as has been said a few times) enjoy yourself, if you don't you will have a very short career.
P.s. sorry about the spelling and gramar, its stupid o'clock in the morning