Setting yourself achievable goals will help focus your mind on what you want to get from your Pilates. Make your goals "SMART": Specific, Measurable, Achievable, Realistic and Timed.
Specific: We all want to 'get fitter', but it's more useful to know what particular aspects of fitness you are you going to work on. This also helps to keep your goals measurable...
Measurable: Giving yourself a goal that can be quantified with time, reps, or distance is ideal. This could be as simple as being able to touch your toes in a forward bend! When you can measure your progress towards your goal, you will be motivated to keep working at it.
Achievable: Get help from your Pilates teacher to identify goals that are important for you, and how to reach them within your range of abilities and within your budget.
Realistic: If your goal is measurable and achievable it is also likely to be realistic - you need to be able to get there as the person you are today, not as an imaginary perfect version of yourself.
Timed: Without a deadline you are less likely to succeed. Thinking about when you want to achieve your goal will also help you plan how you will fit your Pilates practice into your life.