You are right to be concerned about avoiding other traffic, but you are also right to be concerned about being overly concerned, as it were.
I also went through the same phase, there were quite a few occasions where my instructor tapped me on the shoulder to point out traffic which I hadn't seen. There were times when I must admit I felt a bit of a numpty for having missed something which was so obvious, to the point that I was wondering what would happen when I was solo - how was I going to fare then, and who else would I miss?
In the event things have turned out fine. There have been occasions where I have spotted aircraft rather too close to me, but things never got to the point of panic stations and I was fine. There were even occasions where I spotted aircraft which my instructor missed (but there weren't many of these..
).
Some tips spring to mind:
You don't need to complete stuff like cruise checks and pre-landing checks all in one go, its OK to do them in stages to ensure that you don't lose track of what the plane is doing
I was taught to scan the sky; focus for a couple of seconds on a patch of sky then move on to another patch, moving from one side to the other.
You're flying a C-152, don't forget to have a peek under the wing when entering a turn (you'll need to lift the wing to do this)
Use radio calls to identify the position of other aircraft and where they are going, there is a real knack to doing this. This is a very good reason to listen in on local frequencies when in the cruise, but always try to play the game as well by letting people know where you are so they can avoid you too (interestingly this is a good reason why I don't use London Information as the service is basically a waste of time, have a listen in one day for exciting information about aircraft 70 miles away!
)
Oh yes, don't become fixated on one 'target', you'd feel pretty stupid if you gave aircraft X a wide berth as you collided with aircraft Y...
Good luck!
[ 16 November 2001: Message edited by: Bluebeard ]