The speaker of "Lost myself" is looking back on a relationship that ended badly. They describe giving their partner everything in a clear order: happiness first, then the heart, and finally the soul. Each step goes deeper, so by the end there is nothing left to give. Then comes the blunt question, "And what did you do?" It sounds hurt and a little angry.
The answer is simple and painful. The other person promised love, then took it back. The speaker is left "living without" what they handed over, which suggests they feel emptied out, as if parts of themselves are gone. The title fits that feeling: giving so much has made them lose who they were.
The mood is sad and raw, but not bitter all the way through. The short, plain lines sound like someone speaking quietly after the damage is done. The last lines add a fragile hope that what was lost might one day return, which makes the ending more sorrowful than hopeful.