Visualise your life without the things you love

Practice "negative visualization".
This is the most valuable technique taught by Stoic philosophy. To truly appreciate what is dear to you - both moral and material - imagine your life without them.

Practice daily appreciation for the people in your life and for the material things you currently possess.
Paradoxically, by wanting more, you will inevitably become even more dissatisfied with what you have. The action of writing in a daily gratitude journal, for example, will put things in perspective.