Sleep training

I decided when my baby turns 4 mo which is in 10 days im going to sleep training him. I am soooo sad already just thinking about it makes me nervous i cant see him crying i know it’s going to be really hard for the both of us but it’s going to be worth it. The reason im thinking about doing it is because im so tired hes never been a good sleeper, he just want to sleep on my bed with me or on top of me, next month im going back to work and i need him to learn how to self soothe when he’s at daycare because otherwise i know he will cry even more...