I have multiple projects on the go, but thats just the way I operate. When I am cooking, especially baking, I will have two or three things on the go at once .... eg: Make up a waffle batter - let stand, make a batch of ginger biscuits, while the first tray is cooking start up a muffin batch, put second tray of biscuits in oven, get out waffle iron- start preheating, biscuits finished, put muffins in oven, start cooking waffles, take muffins out of oven, finish cooking waffles. Hubby bemoans the amount of washing up I create, but I often comment that I don't just cook, I CATER!
I will do the same with my sewing. Its nothing to have up to 6-8 projects cut and stacked on my sewing table, and I will switch between clothing, quilting, xmas gift sewing, bags .... not to mention that I will have the embroidery machine trundling along at the same time (I sometimes wonder what I am doing to my hearing).
But, this sort of excess requires space, and if you are short of space, then restraint may be called for.