Get a small notebook and take notes on how much you spend and on what, whenever you are depressed. Also take notes of the things you buy when your not depressed. Pay special attention to the days that you are not depressed. This will help determine how much you are able to set aside for days that you are.
Create a separate savings fund for the times that you fall victim to depression. This could be anything from an envelope, to a jar, or another account. This separate fund will keep you from fishing into your savings whenever you are down. Determining how much to put into that extra fund is entirely up to you. But please make it realistic. Don't put too much into the fund if you know you have bills to be paid and other priorities that require immediate financial attention.
Lets say that you receive $400 dollars every paycheck, and 25\% of that goes towards your savings, while the remaining 75\% goes towards spendings. Try to take 10\% of that $300 dollars and put it into the depression fund. If bills are not tied up, you can add a little more to the fund or your savings account. Try to maintain a coin jar to help build in money also. Cash it in later to add to the fund.
Be prepared for those downer moments. Is there something you noticed you like to buy whenever you are depressed? Some people tend to spend more money on food whenever they are depressed, so try having some of your favorites already stored in the house so you wont have to buy them when those moments arise. Try saving your treats more for when you are depressed so that they will be there when those times come. Don't look forward to being depressed just so you can eat that double dunked chocolate-chip ice cream.
Help yourself;everyone deserves to feel good about themselves. In order to save your money and mood. Try to find out what triggers your depression, and take action to reduce the outcome of being depressed. Try activities that doesn't include spending money. Sew. Make your own clothes when your down, instead of buying them. Visit the beach and take long strolls to help ease and clear your mind. The scent of the sea breeze and the soft sands can be therapeutic to the mind and sole.
Try finding a self-help community through online forums, and share your experiences with others. You can feel a lot better knowing that someone is there to relate to your feelings and money spending habits. Involve yourself in activities that generate income, like a community bake sale. Keep your mind busy.
The whole idea is to reduce spending and to have better days.