Money rarely brings out the best in us.
It triggers us. When we are triggered, we react in ways that we wish we could take back. Here's to second chances.
When you said, "You spend too much," what you meant to say could have been:
"I am worried about our financial situation." Whether you are worried because your situation is dire or because your investments have fallen or because you are uncomfortable with money, you are worried. By accusing your partner of spending too much, you get to take the focus off your own discomfort and thrust it upon them.
Or, "I wish I felt more successful." You don't think your partner is frivolously spending, but you might feel like you don't earn enough. Their spending triggers a sense of discomfort in your own choices. If they earn more than you do, then their spending reflects on feelings about your unequal, and possibly uncomfortable, financial contribution to your lifestyle.
Or, "I feel like your spending is in response to frustrations with me." Rather than talk about what is going on in your relationship, you act out in ways where your money can be the focus. You can point out your partner's spending rather than look at how distracted you have been or how unsupportive you are at this stage in your life. It feels to you like spending is in reaction to you rather than in support of both of you.
Some people overspend, but the conversations that focus simply on the spending are probably not getting to meaningful partnership issues.
When you said no to something your partner wanted to do, what you meant to say was: