I'm not interested in why what you did wasn't actually as cool as I may think it is, or how what you did wasn't actually that hard, or how you weren't the only who got the grade/raise/promotion that you did. I want to celebrate you, and I want you to celebrate yourself.
That's where this discounting comes from, right? We don't celebrate ourselves and then it's hard to receive praise or congratulations from others. That isn't humility, that's diminishing our accomplishments and choosing to keep ourselves down.
Acknowledge yourself and the effort you have invested. Doing so will allow you to (A) be proud of yourself and satisfied with what you've created and (B) provide the foundation for your next heroic act.
Praise or celebration may never come from others, but it can always come from within you. Acknowledge the wins and the effort invested, no matter how small. Don't discount, account fully for who you are and how you show up in this world. I thank you and celebrate your contribution.