Why is my plant drooping?
Drooping is genuinely ambiguous — both too little and too much water produce it, because both end with roots that cannot deliver water. Do not water a drooping plant until you have checked the soil.
The causes, and how to tell them apart
Thirst most common
How to tell: Soil is dry two inches down, the pot feels light, leaves are limp but still their normal colour. The plant perks back up within a few hours of watering.
What to do: Water thoroughly. If the soil has shrunk from the pot, bottom-water so the rootball rehydrates rather than the water running down the gap.
Root rot from overwatering common and serious
How to tell: Soil is WET and the plant is drooping anyway. Stems may be soft near the soil line and the pot can smell sour. Watering makes it worse.
What to do: Unpot and inspect. Trim away brown, mushy roots, repot into fresh, fast-draining mix in a pot with a working drainage hole, and water sparingly until new growth appears.
Transplant or relocation shock temporary
How to tell: Started within a few days of repotting, moving house, or changing the plant’s spot.
What to do: Keep conditions stable and wait two to three weeks. Do not fertilize a shocked plant and do not keep moving it looking for a better spot.
Temperature stress seasonal
How to tell: Sudden droop after a hot afternoon or a cold night, often with no change in the soil.
What to do: Move it out of direct afternoon sun or away from cold glass. Water in the early morning during heat, never at midday onto hot foliage.
By species
The likely answer differs by plant — these species have their own version of this problem:
Plantroster compares this month's photo against last month's, so slow changes — the ones you stop noticing because you see the plant every day — get flagged.
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General horticultural guidance, not a diagnosis of your specific plant.