How can I make an automatic door that opens for me only?

Use something like this:

Into the command block put this command:

testfor @a[x=X,Y=Y,z=Z,r=R,name=NAME]

X, Y and Z are the door coordinates (lower half), R is the radius of the testing area in blocks (for an equivalent to a pressure plate put 1) and NAME is your username.

All repeaters are set to minimum delay, esp. the clock on the right. Under the door is a Redstone torch. This will only work with the comparator - MC 1.5+.

Since the device is fairly complicated on the redstone, here's a picture:

(Image taken by me)

In the command block, put

testfor @a[r=5]

(Replace 5 with the number of blocks you want a player to be away from the command block until it fires)

Here's a side-by-side comparison to break the command down:

testfor         Powers the redstone repeater if the next part evaluates to true

@a              Targets all players

[r=5]           Narrows 'all players' down to 'all players within a 5 block radius.

To sum up the image: First, the redstone clock (left) should be started. Just place a redstone torch on one side of the repeaters and break it right after.

Then, the command block will be repeatedly queried whether or not there is a player in a 5-block radius. If there is, the comparator will power, the repeater will fire, it will go down to the redstone, through the bottom repeater and power the door.

P.S. You'll probably want to cover up all that redstone. P.S. You'll probably not want to use sand and wool; pick blocks which suit your needs.