So many relationships go to ruin simply because one or both parties are too afraid to say how they feel, and they hold those feelings in until it becomes a nuclear bomb of an argument one day.
If you are too afraid to say how you feel because you are afraid your partner isn’t going to understand you, or is going to be upset, frustrated, or angry with you, then you have never had a real connection with that person anyway.
Someone who really cares about you will care about your happiness over their own; they want to know the truth, they want you to talk to them, they care about making sure you are reassured, understood and happy.