Crying is normal and necessary. Is your dad maybe talking about "inappropriate" crying, like if someone bumped into you accidentally and you burst into tears? When we feel sadness or loss intensely enough tears can be the expression of those emotions, the acknowledgment and release of them, rather than keeping them bottled up inside. If your dad thinks that you cry over unimportant things, that might be worth looking into. If you cry over any little thing, then there are other things going on. But if you cry over the sadnesses in life like the loss of a friend or pet, that's nothing to be ashamed of. Some of the most unhappy people I've known are the ones who aren't able to cry.