Sometimes a "Do it yourself" attitude works quite well. You can be focused on your own concerns, finances, work, play, while I am focuses on mine, and we become better suited in the long-hall - Stronger and more apt without using each other as a crutch. However, there are other times when making personal sacrifices for the needs of others produces a better outcome.
Like, imagine if you and I went to a local McDonalds. I asked you to selflessly refill my drink, while you asked me to selflessly refill yours. It's a win-win, but we might be better off refilling our own respectively because we mitigate the hassle. But, let's say that we refill each other's and we do a better job because we somehow know what's best for each other. Maybe I got you decaf because you would turn into a crazed maniac if you had too much caffeine, and maybe you got me unsweetened because I was turning into an obese glutton. If we hadn't helped each other, then perhaps we would have made poorer decisions for ourselves. This happens every day in the real world. However, it is also quite possible to make poor decisions for others.