There are times when being nice isn’t the best thing to do. I know you want to come across as the world’s loveliest human being, but that is just a lie and you know it. You have to be honest with yourself and her and express how you truly feel 99% of the time, (don’t say hurtful things if it is not necessary).
You need to let a girl know when you are upset with her, in order to stop her from thinking that you are a doormat. But, the main reason is to prevent yourself from being treated in a way that you do not wish to be treated. I know that you do not want to hurt her precious little feelings, because you don’t want her to get upset with you (because you are scared of the relationship ending, (because you are scared of being alone, (because you cannot stand not having attention and affection.))) But please… If a girl is taking you for granted or being disrespectful, you need to tell her you don’t like it. Not only should you tell her you don’t like it, you should explain to her what, how and why you feel the way you do.
For example, if the girl you are seeing is very obviously flirting with another guy, (and you had said this is not allowed in the beginning) and you are not OK with this, then you should express your anger (not physically). In this situation, you shouldn’t be afraid of making her cry, because crying is a good sign that she has recognised she has done something wrong. Think of it as taming a lion… when it behaves badly, there must be some sort of punishment, and this is the best punishment you can give.
A lot of the time, you really should not express (or feel, if I am being honest) your anger towards a girl. The most common scenario is when a girl is not interested in you. If you show any anger towards a girl that is not interested in you, she will think that you are desperate and bitter, as someone who has a satisfactory amount of attention from women in their life would not care if one person is not interested. To clarify, showing anger in this situation shows that you do not have a satisfactory amount of affection or attention in your life, which in turn, gives the red flag that in a relationship you could be very needy and so your potential of being a boyfriend is decreased.
I know how frustrating it feels when you have been single for so long, hunting, searching and looking for affection and attention everywhere you go. The thing is, that feeling will come across in your communication and you need to resolve this problem. You must be very content without others. In order to do this, you must remove the need for others to give you any sort of ‘warmth’ or appreciation in any way. You must be content in yourself on your own in order to have a healthy relationship with someone else. This works with my philosophy on attraction.
To summarise, if you are too nice, you are a doormat, if you are too bitter, you are a leech. Look after yourself x