money from steemit upvotes is not earned income, not even capital gains. The reason is that you are not paid for your blogging with currency, but rather new shares (steem) generated by "Steem company".
Only after you change those shares to Euro, it becomes capital gains, which has different tax rate than regular income from work as well.
Perceive your blogging rather as marketing activity. That is investment and investment is a under expenses, not revenues.
As long as you pay taxes from your regular job, you give value to society and pay some share to NL government.