Am I right to break up with another person if I am losing interest?
That seems like the correct thing to do. Is it something you feel guilty about?
A bit yes, but that was because she likes me a lot and I like her too
It's completely understandable to still be in love with your partner that you will break up with, but you are being really mature if you know it's not going to work out in your commonalities and interests. Staying could only prolong your boredom.
I will do it next time i lost interest and feel a bit tired of that person. But I can get over the guilt in next few days.
Sometimes you may like a person, but not have much in common with them romantically. In these cases, ending the relationship is better than stringing her along when you know you've lost interest.