In my opinion... in Buddhism this kind of worry is called "udacca-kukucca" :) -- "Am I not doing enough of what I should be doing? I am doing this but shouldn't I be doing that instead?"
Instead, the perfect mind in Buddhism is A) free of the conflict between "this" vs. "that" and B) makes the best use of any situation.
So if real situation presents itself when someone needs help, and you see how you can help - go ahead and help. But if there is no situation and no clear idea, then it's just worry. Especially when you are meditating - all kinds of thoughts can come up, but your goal is to keep going.
So it's not about prescriptive guidance: "you should spend 50% of your time helping others" - but rather about doing your best as you're letting your life unfold.
Of course we have all these grand ideas about the great business we want to open, or the great way we could help people, or other visions of great success - but they are only projections of thought into the future. This projection creates a mismatch between "here" and "there". From this mismatch comes dukkha, the feeling of wrongness.
Instead, for any success you will have achieved, there must be a pathway from where you are now, to there, with the first step being within reach. Therefore the only way to get there is to work with what you have right here and now. So do your best with what life gives you at every given moment, acting with most compassion, most openness, most wisdom, most sincerity etc. - and you will get to the best possible place you could have gotten to - and on the way there you will have many chances to really help someone - and it will be real and within your powers - and not some abstract idea that generates dukkha :)