Sacrifice requires discipline. Christ calls us to disciplined, sacrificial, cheerful giving. Develop a habit of sacrificial giving. That varies with individuals and cultures. I suggest that 10 percent of one's income is only a starting point for most Americans.
Good habits are invaluable.
A habit of sacrificial giving will make giving easier and more joyful in the years ahead. With a pattern of non-sacrificial giving comes the habit of not trusting God and not treasuring His kingdom. The path to joy is in losing our lives for Him. If not, start immediately. This is one of the three most significant areas of Christian obedience.