If you gamble everyday then yes you will lose in the long run. There's no denying in that. The house will always be the more profitable party in gambling. This is why it's best to gamble just for entertainment and when you can afford it.
If you gamble 7 days straight or one day/month for 7 months it's basically the same thing but you're doing it slowly.
on the long run means after a long time, no matter if you play it daily or weekly or monthly. The problem is that it's hard to control the amounts of money we put in casinos, because for example putting a penny for each bet would mean an unconsiderable loss. If we can control the sums we put in the best, winning won't be a problem at all.