Besides the fact that it is not very nice to be thinking about someone else while being intimate with another person, doing so can actually prevent you from experiencing tantric sex. Comparing people and things is normal. However, when you compare what is happening now to what has happened in the past in your bedroom, you make it very difficult on yourself to learn to accept new things.
If you expect your current partner to touch you in the same manner as your old one, then you are pretty much expecting something that is highly unlikely to occur. As you make the realization that your current lover’s touch is not the same as your ex’s, you are likely to start thinking about it obsessively. While being touched by your partner, you are likely to wonder things like why they are touching you in a way that is so different from your previous lover. This makes it impossible for you to truly feel your current lover’s touch, and that is definitely not a good thing.
Humans are creatures of habit. That is why you come to expect certain things in the bedroom. However, if you can move away from that, you will be able to open up a world of possibilities.