Cant stay hard during sex

i get hard before n start of sex then start getting soft, how do i start hard?

I could be wrong but your over thinking you need to relax and enjoy the moment make sure your ready and your partner is ready because if you have it on your mind then you make your self become soft by overthinking it because I am guessing this is a if but do this happens when you watch porn if not then you just have a mind problem but I am not a professional but I got a lot better from this app it helps for real