>tfw still miss my ex-girlfriend after 5 months and no amount

Tell yourself "I accept the fact that I still like my girlfriend. I am not smaller/weaker because of that."
And drop the weapons. Stop fighting the feeling, let it roll, let it flow, right out of you through time. Everytime it bother you, take a deep breath and tell yourself the above.

Also, there's this EFT thing, a practice that is said to remove unwanted emotions. Check it out online, the full name is Emotional Freedom Technique.