I would argue ability to provide a service is in it's self an abstract form of capital.

Time, energy and willpower can also be viewed as a capital. There's a reason business owners will pay people to be doing work they could easily do themselves. And I think it's important that we as a society recognise that any time or energy spent transactionally should be properly compensated.

Of course we shouldn't fall for the trap of trying to maximise and optimise every last ounce of capital in our lives, its important to learn to let go of our posessive human nature. But we should appreciate when we are giving and taking things to and from other people.