Restlessness in practice after a retreat

The suttas are specific about agitation: a restless mind is the wrong occasion for pushing investigation and energy, and the right one for cultivating calm. Soṇa's lute, strung too tight, will not play in tune. Post-retreat restlessness is often integration doing its work rather than a hindrance to defeat. If it doesn't ease over weeks, or if it comes with fear or disorientation, that is a conversation for your teacher, not for a passage.

What the suttas say

“But when your harp’s strings were tuned neither too tight nor too slack, but fixed at an even tension, was it resonant and playable?” “Yes, sir.” In the same way, Soṇa, when energy is too forceful it leads to restlessness. When energy is too slack it leads to laziness.
The classic instruction on balancing effort.
AN 6.55:6.1–7.1 · With Soṇa
In the same way, when the mind is restless, it’s the wrong time to develop the awakening factors of investigation of principles, energy, and rapture. Why is that? Because it’s hard to settle a restless mind with these things. When the mind is restless, it’s the right time to develop the awakening factors of tranquility, immersion, and equanimity.
Which factors to develop when agitated versus sluggish.
SN 46.53:12.1–13.1 · Fire
Still, thinking and considering for too long would tire my body. And when the body is tired, the mind is stressed. And when the mind is stressed, it’s far from immersion.
The Buddha on overwork before awakening — even wholesome thinking, kept up too long, exhausts the body and then the mind.
Where this stops: Said of wholesome thoughts pursued too long; it is about pacing, not a warning against reflection.
MN 19:8.8–8.10 · Two Kinds of Thought
Take a mendicant who is focusing on some subject that gives rise to bad, unskillful thoughts connected with desire, hate, and delusion. That mendicant should focus on some other subject connected with the skillful. As they do so, those bad thoughts are given up and come to an end. Their mind becomes stilled internally; it settles, unifies, and becomes immersed in samādhi. It’s like a deft mason or their apprentice who’d knock out or extract a large peg with a finer peg. In the same way, a mendicant … should focus on some other basis of meditation connected with the skillful …
Concrete methods for a mind that won't stop.
Where this stops: These are graded; the last, forcing the thought down by sheer effort of will, is a last resort.
MN 20:3.1–3.5 · How to Stop Thinking
“Good fellow, how did you cross the flood?” “Neither standing nor swimming, respectable sir, I crossed the flood.” “But in what way did you cross the flood neither standing nor swimming?” “When I stood, I sank under. When I swam, I was swept away. That’s how I crossed the flood neither standing nor swimming.”
The shortest statement of right effort in the canon.
Where this stops: About effort in practice, the crossing itself; not a picture of caring for someone. Never use it to tell a tired carer they are straining or should stop.
SN 1.1:1.4–1.9 · Crossing the Flood

Bring your own situation.