It's far easier to defend one player on the counter attack, than 4-5 players. You'll always get caught out occasionally, that's football, no team is perfect.
You reduce the chances however if you have a strong counter attacking threat yourself, as teams are scared to attack you knowing one mistake can lead to their downfall. They're more likely to sit back and not take the risk, which is exactly what we want, so we can control the entire game.
The defence needs to be improved no doubt, but strengthening the attack will prevent the defence being as exposed as often. Hence the term attack is the best form of defence.