A little tip I use regarding the mental side is to never doubt in your own mind whether you will finish or not. You have paid your money, done your training and you will finish.
If you set it in your head that the only reason not to finish would be injury it makes things easier come race day. In the middle of the night when your having a rough patch, feeling tired and ready to quit you can remove those thoughts from your mind easily because they are not options available to you.
Positive thinking is massive, if you go in thinking there is a chance you may not finish its too easy to use that excuse later on and end up pulling out. Tiredness really isn't a reason to DNF.
Torq i usually use a crew but i always have a night kit. So as the night comes in and the temp drops i change. You will be amazed how cold you will feel in the night even if its mild. The more worn out you are the colder you feel.
Also mentally it sets you up for the next phase of your race.