Critical thinking can help you to make better decisions because it can prevent you from making decisions based on hunches or gut instinct or faulty/inadequate thinking.
The most important thing that critical thinking does for you is to force you to think through your decision. If you are thinking critically, you have to examine the assumptions that you hold going into the process of making the decision. If you have people giving you advice or trying to push you one way or the other, you need to be able to analyze the extent to which their input is biased. You have to be able to think through the possible consequences of your decision, being very careful to think of all the ways that the decision might impact your life.
If you apply these skills and techniques, you end up with a decision that has been well thought-out. You do not simply make snap judgements based on preconceived ideas. You do not blindly follow what others say. Therefore, critical thinking will result in better decision-making than you would achieve without critical thinking.