Negative emotions are part of life and essential. Don't you think a person would never be strong if he/she doesn't have any experience of negative emotions? There is a saying that hardship makes us strong. That's how negative emotions lead us to have more emotional resilience.
One thing we mistake very easily that we think feeling good should be a 24/7 type of thing. But in reality, it's not possible and should also not be that way. Life would not be as pleasurable if there are no negative emotions. That's why it's perfectly okay if you are feeling sad.
Now let's expand our understanding!
Suppose someone broke your heart. Now you are supposed to feel sad, unhappy, cry and heartbroken. It's totally fine if you do so. There's nothing to feel guilty about, blame yourself to feel that way.
We have to understand that negative emotions, expressing and experiencing them doesn't make us weak. Rather it actually gives us life lessons and we can choose to be strong afterward. There's no place to feel guilty or blame ourselves to feel sad or cry for someone or something. What matters most is what we learn from it and how we proceed.
So from now on, if you feel like crying, cry. Don't bother what social standard is, what people expect from you. If you don't want to show it to others, make some alone time to let yourself express your emotions. Don't hold back, don't feel ashamed for it. Know that it's okay and it's actually necessary.