Keeping a good card habit can increase the credit card limit of the postal service, because it makes the postal bank think that users are responsible and reliable users. Repayment on time every month shows that users have stable cash flow and good planning ability, which reduces the risk of Postal Savings Bank. Not exceeding the time limit means that users attach importance to credit and abide by the contract, which will increase the trust of the Postal Savings Bank to users and thus provide a higher credit line.