How do I break a bad trading habit?

I have this mental block from buying in higher than I have sold. For example, I buy XYZ for 10$ and then sell at 11$, but then a month later it is trading around 12$ and I see a good setup, but this stupid mental block prevents me from buying in higher than I sold.

Any suggestions? Thanks.

Maybe you think of the market as being expensive or cheap. That wrong assumption may be the cause?

If you believe someone is willing to buy at $13 why not buy at $12 and sell to them at $13.

change your holding period

Probably comes down to you maybe not being entirely sure why it was a buy at the lower price. If you knew that, you'd be able to tell if it is still a buy at a higher or lower price. Can you explain to youtself concisely why it was a sell at $11 and a buy at $12 a month later? Try writing it down.