Imagine the downtrodden, sad, lonely, dispirited, and ulgy Betty. Think of her posture. Her head hangs, her chin on her chest, her shoulders droop.
Suck it up!
She straightens her shoulders, inhales deeply and fills her chest, pulls her head up and back.
She has just sucked it up.
And no, there are no vulgar connotations in this context.
- For Teachers