Maintaining very high temperatures, maintaining a magnetic pinch that is opposite to the magnetic field produced, maintaining a material feed into a strong field that opposes it, and so on. Fusion works in stars because gravity holds the constituents together during the fusion process; and, the high temperatures don't dissipate into the immediate surroundings.
My professors also said that the nuclear furnace would produce all sorts of atoms ranging about the periodic table. Most would be unwanted and would result in dangerous wastes.
A fusion reactor vessel has need to be SMALL because of those very reasons. Building huge voluminous experimental tanks like the one in the picture is essentially working at cross-purposes to your stated goal.
There will be a fusion reactor built fairly soon, but it will of necessity be small, probably smaller than a microwave oven..................
Think about it, if those humongous tank reactors actually worked for any length of time, they would melt. A small, fully functional vessel can be controlled and cooled a whole lot easier than a huge donut tokamak.
Each unit’s output can be paralleled together with others to scale up the output for industrial use. The small home-size unit would be like your HVAC sitting outside your house in the back yard............