As a psychotherapist I cannot pretend that there is a simple set of instructions that guarantees happiness. We all come from a distinctive combination of genes, and have had a unique set of relationships and experiences that formed us to the shape we are in now; one size does not fit all. But there are underlying principles that can help us.

When it comes to our brains, all humans are born prematurely, as many of the neural pathways in our brains are formed after we are born, and in relationship with our earliest caregivers. If they do a good job, manage to soothe us regularly when we are upset, we eventually internalise this process.

We also need our parents to validate our various moods and mental states in a safe way as we grow up; acknowledging when we are hurt, in pain, or joyful. This allows us to develop all parts of our personalities. If some of our moods are punished or ignored, trouble can arise later on in life.

As you learn together with your earliest caregivers how to regulate your emotions, your brain will be making lots of new pathways that are necessary for you to learn to become comfortable with your emotions and manage them for yourself. Your earliest bonds also serve as a model for all subsequent relationships, teaching you to form nourishing, enriching, and mutually beneficial relationships throughout your life. The bulk of these neural connections happen before you are two years old. In other words, much of the wiring up that determines how you respond emotionally and conduct relationships, happened pre-verbally. The logic, reason and language part of your brain develops so slowly that most of the patterns for how you feel are formed before you can reason with yourself and others.

If your relationship with your early caregivers was less than ideal, or you experienced trauma so shocking it undid the security established in your infancy, it is possible that later on in life you may find yourself in emotional difficulties. But although it is too late to have a happier childhood, that doesn't mean you can't be happier in the future. Your brain is fairly plastic and you can make new neural connections to change that chemistry so that you can improve your self-soothing, self-regulation and how you behave in relationships.

How do you do that? There isn't a foolproof prescription – if you are in a downward spiral you need to interrupt that spiral with medication, or a different set of behaviours, or something else. I'm being vague on purpose; what works for me might not work for you. But there are four underlying structures for positive change:

1. A safe, trusting, reliable relationship that is for your sake. Not necessarily a romantic relationship, but a nurturing one (it could be with a therapist, or a teacher). We are formed in relationship – so the easiest way to re-form is in a relationship.

2. Positive stimulation – good stress. Enough to push you to learn new things, but not so much it tips you over into panic. Good stress enables new brain connections to be made and a plastic brain is what you need for personal development and growth. Examples could be learning to play a musical instrument, or a new language.

3. Develop your self-observational side. This is an accepting and non- judgmental part. It acknowledges emotions but gives you space to decide how to act on them. This part listens to and brings together your emotions and your logic. To help, try keeping a diary, or practise meditation, get used to noticing your feelings and thoughts without judgment.

4. A fresh perspective on your personal narrative. Because so much of our self is formed pre-verbally, the beliefs we live by can be covert. It is important to view your life from fresh angles and to let go of fixed ways of defining yourself. You may have beliefs that start with, "I'm the sort of person who . . ." or "I always . . ." these might benefit from a rethink and possibly rewrite with a trusted person or group. For example, change a message such as, "I must meet my soulmate before my life can really start" to, "What happens when I notice the negative thoughts I have about other people, but don't act on them – what changes in how I then relate to them and how people relate to me?"

These four processes are a framework for change. The content will always be different for each individual Finding out about that content and how to change it? Over to you.

Philippa Perry is the author of Couch Fiction, published by Palgrave Macmillan, at £12.99. She is giving a talk, How to be Happy, at the ICA on 27 January, at 6.45pm.