“When the thought of this brings you more dread than joy it’s time to move on.”
The many responses hopefully gave this user the answers they were looking for.
Note: Some responses have been edited for length and/or clarity.

“I ask myself if I could be happy with this person forever.
‘Am I waiting for them to change?’
If I wait for them to change, I’m relying on something I can’t control.

I’ll become resentful, and they’ll resent my attempts to change them.
At that point, I leave.
They can change or not, but I am in control of my happiness.

I can look for someone who makes me happy.”
“Daydreaming about being single and how less stressed youd be.”
u/2zoots
3.

“If you prefer to be alone rather than in her company, it’s time.”
u/pxl_ninja
4.
Thats when I knew."

“When you are not respected, and either side does not give the relationship priority.”
u/korean_redneck4
7.
“When you’re questioning why you’re still in it.

“I would also say that sometimes people just come into our lives to teach us something.
u/Ambitious_Orchid01
9.
“When your effort no longer matters.”
u/PolyThrowaway524
10.
“It’s so hard to leave a serious relationship.
“When you’re defeated and think life is easier with them no longer in your life.
Basically, what you’ve described.”
u/Resident-Silver-2423
12.
“When you have more bad days than good.
u/Jdesey9999
13.
Something like 70% good might be tolerable but would merit improvement.
Nobody should expect 100%.
“When it no longer serves you, and it leaves you feeling more drained than fulfilled.”
u/Elita_Lolita
15.
“When respect, trust, and friendship are gone.
Love isnt enough.”
u/Superlolo500
16.
“I should have left my last relationship years before it actually ended.
It ended with her cheating on me.
I understand the difficulty of actually leaving.
If you are constantly exhausted dealing with a loved one, that personal growth will be completely abysmal.”