And yes you will be rejected, many many times. Accept this from the outset, and maybe it will be a little easier for you.
Here’s a little secret for you about human behavior: Faced with repeated failure, it is normal to start feeling down, and then to give up. This makes sense, when you think about it from an evolutionary standpoint: why should a creature keep wasting energy on something that doesn’t work? It’ll starve, when it could have been off eating nuts or roots instead of the tasty mammoth it kept trying, and failing, to get. The increasing feeling of depression is a message that ‘this isn’t working and it’s time to put my energies elsewhere.’
BUT – if you want to get published, you need to ignore this impulse towards depression and giving up. Instead, persevere despite every ounce of your being telling you that you’ll never get published. Be dumb and stubborn in the face of all evidence that you’re not good enough. The only guarantee of failure is to stop trying.
This gets pretty painful, though. There came a point in my own unpublished days that I gave myself permission to give up for a while. I needed a break from the constant feeling of failure, and it was a relief to stop stabbing myself with the knife of rejection, and do other things.
You’re not a bad or weak person if you do give up. All it means is that the emotional costs were getting too high, and you valued your mental health enough to stop the pain.
When your emotional shields have been rebuilt, go back into the fray and try again.