Praying for fresh grace for you. The mindset is, in one sense, good and right. In another, it can be dangerous if you ignore texts like 1 Cor 4:7, 1 Th 5:18, Jam 1:17, . Consider something like this as a good addition (not corrective, as it doesn't address what you're saying heads on).
Personally (you may or may not be able to relate, so take with grain of salt):
When I have overwhelming feelings of failure, inadequacy, pain, my go-to thought is: does God need me? Is my worth wrapped up in my usefulness to God? What about my worth here on the earth to my family, work, church? If my worth is wrapped up in what I do, my sense of despair will multiply when I fail or am unable to perform. This is why the gospel is sweet indeed, because it speaks a better word about where my worth comes from: the cross.
The Things of Earth: Treasuring God by Enjoying His Gifts https://www.amazon.com/dp/1433544733/ref=cm_sw_r_cp_api_glt_fabc_MFZN40DXATANAMMTY6NK
There is an excellent book by Joe Rigney titled The Things of Earth that addresses this exact concern, and if you are miserable because you are stuck on this issue, I highly recommend picking it up.
Here is the Amazon link: https://www.amazon.com/Things-Earth-Treasuring-Enjoying-Gifts/dp/1433544733
Otherwise, know that your mother misunderstands what it means to love the world. James 1:17 explains that every good gift is from God. That means the things in life (which include the things of this world) that are good and are meant to be enjoyed come from him. How are you not supposed to enjoy the good gifts given by your good Father in heaven?