Sleep training doesnt stick

Hi all, my baby was a great sleeper until he hit 6 months. Now he is waking up every night at least 2-3 times. We tried Ferber but i feel like he was good the first couple days and now he is back to waking up again. I hate letting him cry! And if we let him, he can cry for 20-30 minutes. He hates naps during the day. I dont know what to do.