Try and plan ahead so that you can win future rounds. You can win and play cards to your palette so you’ll be in much better shape for future rounds (for future canvases). Those cards either keep below 4, play the Red7, or play a run, etc.

Try to add a card to your palette each turn, maybe more than one to the palette if you’re able. If you can change the canvas, consider playing a card to your palette 1st. That card played to your palette won’t take away from any canvas that follows, and may very well enable you to restore your lead.

Any winning card played to the canvas ends your turn, so don’t miss the chance to add card(s) to your palette first, but be careful because you can’t retract cards played to the palette. I sometime find that I’ve placed a card on the palette I’d intended for the canvas - too bad, you can’t fix that mistake.