"The same concept on a poster, a screen, and a social post are three different design problems."

Do this now

Take your current concept and apply it to one specific format. Before opening any software, sketch the layout by hand. Consider what changes — hierarchy, scale, reading distance, interaction — when the format changes.

Unpack

Format is not neutral. A poster is read from a distance in motion. A mobile screen is held in a hand and scrolled. A social post competes with hundreds of others in a feed. Copying a design across formats without rethinking it produces work that fits nowhere properly.

Draw it.

Fast and messy is better than perfect.