It's hard to quit something you put so much time and money into.
This is because of the sunk cost fallacy.
This fallacy occurs when you make a decision based on a past investment instead of a future outcome, such as continuing a bad relationship because of how long you've been together.
We experience this fallacy with a lot of things:
It's a trick our mind plays on us to continue usually unhealthy choices. Why should we stop when we've invested so much time into something?
Examples of Sunk Costs in Your Life
You might stay with a partner who sucks the life out of you for 2 years longer than you should have just because you spent one year together already when the relationship got rocky.
You might continue a career path for 20+ years that you hate just because you majored in it in college and didn't want your degree to "go to waste".
You might live in a house that makes you depressed and poor for more years than you'd like, just because you've lived in the house since you were a kid.
Life is about change.
If you're not willing to realize what is unhealthy for you, then you are falling for the sunk cost fallacy. You're giving up your future happiness for your past time invested. Who cares about the person you were in the past? Let go of that person -- especially if they are unhappy in the present.
You don't have to keep trying to make every situation "work".
Sometimes the best solution is just to avoid the situation altogether.