the circuit is a stressy environment to be in,
relax 
hahahaha!
OK, I totally agree with the sentiment, but thinking back six weeks to when I was in digital.poet's position, it would have seemed absurd at the time! The relaxation only came when I'd got enough of the actions into motor memory that my brain had a chance to drop out of panic mode for the first time - shortly after which, the instructor got out, of course.
The time I *needed* to remember to relax was on about third solo, when my brain utilisation on the flying had dropped so low that I started to notice I was still excessively stressed. I guess a high stress level had become a conditioned reaction to solo circuits. Felt a bit spaced and had to control my breathing, but got it all under control.
In reality you have plenty of time to go through the checks.
Only once they're sufficiently familiar that you don't have to spend 5-10 seconds on each one, trying to remember it and perform it. Took about two sessions (12 circuits) before I got there.
The trimmer is your friend
Absolutely. I found it needs a surprisingly fine touch on the trimmer to get it accurate, though. There is a "dead zone" on the trimmer of about half a turn, in which I can't feel much change in yoke pressure (PA28-140): but that half-turn makes the difference between being two hundred feet low at base, and two hundred feet high.
So I have to trim off the pressure, let the aircraft settle for a few seconds, then see what it wants to do: then apply a further correction. Also sometimes have to adjust power again as the engine speed and air speed change, as the aircraft settles into level trimmed flight.