No! Don't use gmail to store your passwords. Regarding gmail, I don't trust Google, so I won't give Google an opportunity to see ALL of my passwords. I don't want other people to see my passwords. If I wrote myself an e-mail, then probably whoever is maintaining Google will be able to see it, and if Google gets hacked, then someone else, or a lot of other people will be able to see my passwords. I think it's possible that Google could give my passwords to someone else without acquiring my consent.
I use sticky notes, and I write my passwords on it.
If other people go near your sticky notes, then I suggest you hide it, and don't keep in a place where other people can see it.
If you want, you can use a small piece of paper, and you can write your passwords on it. The paper does not have to be sticky. I recommend you don't keep it in a place where other people can see it.
I can think of millions of places where you can hide your passwords. I strongly recommend that you never put your passwords on your computer. If your computer gets infected, or hacked, then someone else might see your passwords. If your computer breaks, then you might lose your passwords, so I think it's a bad idea to put passwords on a computer.