The problem is: When I meditate and reach to a level, I get stuck by the memories of my ex-girlfriend and that stupid relationship I was into (was cheated and was left emotionally/mentally unbalanced for two years) and I just can't pass that stuff. It drags me and there is guilt, shame, embarrassment (rage has subsided to an extent). Whatever object of meditation I'm into, the memories just come and take me with them. I have realized that to make any progress further, I need to win over that episode of mine.
Is it concentration or insight practice you're doing? Could you describe "reach to a level" a bit more?
It pretty clear that this issue is something of a stumbling block for you, but it might be useful to investigate what's feeling "guilt", "shame" and "embarrassment", look at what sensations make up those patterns and observe how they're subject to the Three Characteristics:
Emptiness/No Self: If you can observe them then they can't be the observer, they can't be this sense of a self, they are not you. If you can name and objectify the guilt, the shame, the embarrassment then they cease to be able to affect you in the same way because you can experience the simple fact that there's no self to be found in anything in the observable universe.
Impermanence: Every single sensation which makes up our sensate experience lasts no longer than a split second, by seeing this clearly you can begin to let go of the clinging to the memories of what's gone past. Each emotion is made up of dozens of mental and physical sensations, the content is secondary to the sensations themselves and if you can understand this, see it for yourself through insight practice, then you will get past this.
Suffering: I know you're probably thinking "Fuck you, I know all about suffering otherwise I wouldn't be feeling this way", but this is something fundamental and not the literal "This sucks" feeling caused by an unpleasant situation. If you've read MCTB then all this stuff should be obvious already but if you can learn to see the suffering inherent in every single sensation then you can see how the way you're feeling right now is being created. Easier said than done, but this is what does the damage.
Remember what Daniel talks about in his book about not getting involved in your "stuff" when practicing? The difficulties you're experiencing are because you're doing the exact opposite of this, if you pay attention to this sensate reality as it arises and passes, observe the 3C's in real-time and practicing well then these sorts of experiences can be dealt with efficiently and effectively, leading to realizations which will allow you to understand this much, much, much clearer.
I know that 'Keep Practicing' will certainly is the mantra but any other catalyst or technique I can use to conquer this side of my life. Anybody to give some advice around this?
Aye, keep practicing is really the only way to travel and it's the mantra because it's what works best. The best technique in this situation is observing the 3C's of sensate reality, it works because it cuts through the surface and down into the root of the problem so if you can continually apply this then your practice will improve. Other than that, perhaps alternating insight with concentration practice will afford you some breathing space until you feel ready to really go for it and note this motherfucker into oblivion.
Practice well.