For our case, say it takes you an hour to prepare dinner for your family, to pack lunches or go grocery shopping. Now, it's true you're saving money by doing these things rather than eating out. However, how much time are you spending on these things?
When I had a job at a restaurant in high school, I would always spend an hour cooking lunch/dinner so I wouldn't have to spend money eating out on my way to work even though eating out was quicker. I can't count the amount of times my manager called and asked me to come in an hour early to cover a shift. I would always say no because I wanted to spend the hour cooking so I wouldn't have to spend money to grab food on the way there. In hindsight, I think I know I made a mistake. I made $8 an hour so every time I turned down an hour of work to make myself dinner, I missed out on $8 that I could have earned. I could have eaten out for about $4. Meaning I could have earned an extra $8 by working, spent $4 to eat out and netted a gain of $4.
Now, by cooking my dinner at home, I was saving $4 by not eating out, which made me feel pretty smart. But now that I look at it, yes it is true that I saved $4 but I also missed out on earning $8, meaning in then end, I was losing money.
What I want you to take out of this story is to make sure that what you are doing to save money is actually worth it. Today everyone is so desperate to save money that it could be actually costing them money. Not every cost cutting idea is actually saving you money, like my idea of cooking instead of eating out. Be aware of the opportunity costs of the saving measures you undertake.