The Cap takes his one way ticket with Iron Man to WWII days and looking for PYM particles. In the process he meets his love his life Peggy Carter.
Though she was within his reach Cap did not reach her, or try to do something through that let her knew his presence. If he did that the timeline will split and lead to further consequences. Cap's pained longing look at Pggy, who was busy with her work is really reaching literary standards.
However, in Endgame, he relinquishes his duty to Falcon, and decided to lead a normal life with his love Peggy Carter. This marks the end of the original Avengers squeals, and a new band of heroes to come. The one way ticket Cap takes with Iron Man to the past, lands him in the WWII days, as one of the shield agents become suspicious he accidentally rushes into a room only to see Peggy.However in Endgame he relinquish his duty to Falcon, and decided to lead a normal life with his love Peggy Carter.