Certainly, if you were to try to maintain this lifestyle over many weeks, you would find both yourself and your work suffering. Endless days of sixteen hours or longer will take their toll on the body. It is quite possible that illness could result if this was carried on for long enough.
Some outrageously long work days are probably going to be necessary if you are to establish your business from a standing start. What you need to guard against is carrying your work ethic to too extreme a degree and obliterating your time management skills. As soon as you are able, you can begin to outsource some of your critical tasks to other capable people. There is also much you can do in the way of automation, where your autoresponder scripts can handle a lot of the work for you.
If you are still stuck at the stage where your business is still literally a one-man business, in that you are performing every single task in your business, then you need to give some long and careful thought to your time management skills in the short term, and in the long term, to how you can move away from this state. If you are making some profits, then you can start to consider the time management skills concept of leverage. Leverage is how the wealthy people of the world were able to attain their wealth in the first place, and it can certainly do an enormous amount for your business.
You can leverage your efforts by employing outsourcers. Note the word 'employing' here is not used in the context of hiring permanent staff, paying them wages, and covering all of the other things an employer has to cover. No, this is simply paying an outsourcer for services rendered. You only pay for the work which needs to be done. If you can get more work done in a day than you otherwise would, then you can increase your profits. If you can pay your outsourcer and still have a profit left over, that is money you would not otherwise have had, as you would not have been able to carry out the work due to the limitation of how many hours there are in a day. Outsourcing is an exercise in good time management skills.
As well as the consideration of outsourcing making you more productive in the sense of having more hours available, you can also consider that you are likely to have more creative ideas if you are able to relax and take some time out. Scheduling in down time is also integral to effective time management skills. The old myth of the one man business chained to a desk has been replaced by a vision of a bronzed figure on a beach with a notebook, controlling his army of outsourcers while the waves gently cover his feet.
