Me suspicious

i think myself to be more suspicious then other people. i never wrote down any of my id s and password. Whenever some new password comes to me in that ubiquitious sealed paper, i just read the password, try to remember it and then i just tear away that paper. It has been too scary for me to imagine my passwords going into some unscrupulous hands. But when i see other people, their laxity in such matters, i feel that may be i am over cautious.
Yesterday only, i saw that SU was keeping his online trading id & password in his valet at the place we keep photos. Anybody can see it easily. There are some other events also when i saw people sharing passwords freely. All this sometimes make me feel myself to be more careful than actually needed.