How do I stop being tilted?

I was researching on a stock which had gone down in the recent times and was really undervalued. Its business was diversified and was good on all metrics so I was considering buying it on the start or the week. But on monday it went up 20% and I missed an opportunity to get into that stock. It has stabilised there and I feel super tilted as weeks of my research has gone to dust. I am torn apart between buying the stock with a premium now when I see that the price is fair valued and not undervalued. Also I think this tilt might get me into trouble and I might start buying stocks out of fomo. How do I get myself out of the frustration and what could I do better going forward