[header] How to get over his past [title] Stop thinking about his past. [step] Sounds a little too simple but in fact its not at all hard. If you find your mind drifting towards his past or his ex try to think of something else. 
You can either substitute your thought with an image, such as that of a loved one or you could simply think about a different topic such as your shopping list. Alternatively just focus on your breathing, feel your lungs take in air, feel it travel through your nasal passage.