The credit card balance is a little bigger than expected. That weekend trip turned out to be a bit more expensive than planned. It seems you owe some taxes this year? That's right you took out that mutual fund to buy a computer. Plus that balance is still there on your other credit card.
The room suddenly feels a little bit smaller.
Don't let the panic set in. Breathe. Re-prioritize your plan. Make the necessary sacrifices. Cancel a few subscriptions. Take out the HD for a couple of months. Well...maybe cancel a few more subscriptions instead. The point is, when new costs come up, or ones you forgot about, you can't ignore them. They will show up at the worst possible time, and probably a few at the same time.
Sometimes its better to clear out those debt balances first before enacting your savings plan. Its very easy to get caught up in the worry of not saving with every pay check. But it is not worth it to continue to carry debts in order to save. The hole will just grow, but at a slower pace. It is the slow growth that you will not notice until the surprise bills roll in.
Clear balances, get back to square one. Build some savings so when the extra costs due occur, or you decide to spend a few more days at the tropical resort, you won't be spending the next 6 months worrying every time the mail is delivered.