2. Use What You Have
In a consumer society, whatever problem you may have can always be solved by buying something else. If something breaks, go out and buy a new one. If something isn't exactly right, go buy something that is. In your grandparents' time, when something broke, they first took a look to see if it could be fixed.
If it couldn't be fixed, before it ended up in the trash can, they would consider whether it could still be useful for something else. There is no reason to go out and spend money on something new if you can get the same thing accomplished with the things that you already have.

3. Doing It Yourself Is the Way to Go
When it comes to fixing things, the first people that your grandparents looked at were themselves. Instead of calling someone to fix something that broke, they fixed it on their own most of the time.
In a society where we now hire people to do most basic repair and maintenance, it's important to remember that most repairs aren't nearly as difficult as they may appear and that you can do much of it on your own with a how-to book and patience.

4. Things Have More Than One Use
People tend to buy stuff with a specific purpose in mind and use it exclusively for that intended purpose. What your grandparents knew is that most things can have multiple uses throughout their useful life. That T-shirt can become a night shirt when the collar gets worn and can't be worn outside, and then a painting shirt when it starts to get holes and eventually rags when the holes get too big.