You might need to ask yourself whether developing the skills required to become head of marketing is realistic, based on your existing experience and qualifications. For example, do you have the time to complete the required training effectively? Are the necessary resources available to you? Can you afford to do it?
Your goal also needs to be realistic and attainable to be successful. In other words, it should stretch your abilities but still remain possible. When you set an achievable goal, you may be able to identify previously overlooked opportunities or resources that can bring you closer to it.