It took a lot of time, but we have been able to save some money and now have a buffer. We do our best to only spend what we have in our monthly budget. The vast majority of the time that works out very well. But sometimes a large expense can't be sourced from our monthly budget. This is where the buffer comes in. We can use some of the buffer money to pay the excess portion of the bill (avoiding credit card interest). We then work to pay back our buffer (from our monthly budget) in months to come.
Saving money for a buffer can be really tough, when there is just enough to make ends meet. Cutting expenses + indulgences is imperative...but another thing that has really helped us build our buffer is that we let the government take more than their share up front. I know there are two ways to think about this:
1. We could use/save that money now.
2. It's easier not to spend it, if we don't have it.
To each his own, but we choose #2. When our refund checks come, we top up our buffer (to the amount we feel wise) and then send off the rest to our mortgage. It feels spectacular!