No question, big decisions are what determine the direction of our life, and, as such, they deserve maximum attention and commitment once taken. However, this evident truth should not bring us into the mistake of caring too little about the small decisions. I refer in particular to those small decisions that we repeat very often in a mostly automatic way, and so form our habits.
If a decision is small but is systematically repeated, the idea that it is small is in fact an illusion. If the result we get is the sum of all our decisions and actions, small but repeated decisions take their part too. For example, if you have the habit to procrastinate, and replace it with the habit to do first the things that you dislike most, this is likely to have a major impact on your life.
Moreover, bad habits often regard "small" weaknesses that we have. We believe we get more results by pressing on our points of strength than by working on our weaknesses, and this is another reason why we are likely to give little importance to some habits. That belief is true in most cases, in my opinion. However, there are also instances (and I am sure you know which ones are for you) where it is an unresolved weakness that keeps us back from growing.
Bad habits for which we do not care control a part of our life. Everybody wants to gain power on the "external" world, but the first and essential power is on ourselves.
To win a bad habit, or to introduce a new positive habit, we need to make an initial investment: this is for the time necessary for the decision/behaviour to become automatic. However, this does not necessarily mean that you need to make a "painful effort" to change your habits. The kind of feeling you associate with the process of working on your habits depends on the significance you give to the experience you are doing and the results you expect to obtain.
If applicable, you can dedicate the next few days just to change one habit, and focus only on that one, all the time you can. This will help you capitalize on the fact that often the same amount of energy if concentrated in a small time brings better results than if spread in a longer time. Another way to is to immagine a dialogue with the habit you want to change. You can keep on discussing in a friendly way till your habit is "convinced" that it is not acting according to your best interest, so the change will appear as a natural necessity.
However you decide to deal with your habits, do not forget to dedicate them the attention they deserve.