Ask Duas in a proper manner because when a person asks Dua which is inappropriate or prays for something sinful; his Duas will not be answered. Don’t make half-hearted Duas. Make your Duas with confidence that Allah will grant them. Especially if you’re asking for something good and beneficial.

Source: 10 Reasons Why Our Dua Is Rejected (https://youtu.be/sEI1SivLQ4c)