painter's block

i bought a large canvas yesterday. 80x80. it's standing in the kitchen on a large easel, staring at me with its white blankness. the ideas tumble in my head...but mostly they are ideas of colors and of fastening bits of wire, beads and some of those rocks with holes in them that i've long been gathering on the beaches of the world. i think i just need to begin already! what's holding me back? why do i feel so cramped about this painting thing? it's like there is a wall of some kind inside me, preventing me from diving in and doing this. why is that? and how can i get rid of it? is there such a thing as painter's block? how can i have it when i'm not not even really a painter yet? arrgh!!! sabin keeps asking why i don't just paint and i can't really answer the question. but i can't paint either...