How do you ensure you don't overspend whilst trying to get ahead in the miles game?

Do not spend over your limit just for the miles. Look at your normal spending habit and plan accordingly. There is no need to force more purchases.

Yes! make sure u spend only what u can afford to pay off end of the month

Only spend on what you need. Then think of what credit card to use to best maximise the credit card miles rewards. It about how your current expenditure pattern can be maximised fully to earn miles. It is not allowing the credit card dictate your expenditure!

1 suggestion , pay your credit card daily or weekly, how much u spend on the day, go home and pay it immediately , when u see ur bank amount lesser , u will feel different.