Can you give any advice on how to get in the right mindset to give significant part of your income to charity? Or did you have no trouble deciding that? I understand how fortunate I am, but I cannot convince myself to give.
I came to the US from Russia at the age of 11; it probably helped me recognize how fortunate I was. Later, learning about the extreme poverty that exists in the world (far surpassing what I saw in Russia) I realized how much more fortunate I was to have had the luck of being born where I was.
One way to conceptualize things is that you are a consciousness that has won the birth lottery - being born into a well-off family, or at least a family in a rich country. I don't believe in souls - this is just a way of thinking; a hypothetical to imagine, akin to "what if I was born a minority, or a member of some persecuted group". The realization that you could have been unlucky may help empathize with those less fortunate.
Branko Milanovic, a world economist focusing on income (inequality) points out that 3 of the biggest contributors to one's income are (a) the country you are born into, (b) the income/wealth of the family you are born into, and (c) the gender. Note that all three are not something one can choose. So the "lottery" of life I describe isn't just metaphorical.
I don't think I would be willing to give 10% of my income if I didn't learn about how cost-effective charity can be. For example, with a $0.50 donation to SCI a child will be provided an anti-worm pill - curing and preventing parasitic worm infections for about a year (see GiveWell to learn more).
I recommend reading the short but super-influential essay "Famine, Affluence, and Morality" by Peter Singer. And after that, read some books by him too.