The 35-year-old faces Australia's Mark de Mori on Saturday in his first fight for three-and-a-half years.
Haye said: "I'm not going to do this if I don't believe I can win that title."
He won the WBA heavyweight title in 2009, lost his belt two years later to Ukraine's Wladimir Klitschko and retired in 2013 with a shoulder injury.
The British fighter weighed in at a career heaviest 16st 3lb 5oz on Friday against De Mori's 17st 5lb 8oz.
Haye's last fight saw him beat fellow Briton Dereck Chisora at Upton Park in 2012.
Haye, who is expected to beat De Mori, 33, said: "If I'm in there and it feels so far away from me then that will be a consideration [to retire again], even if I win the fight.
"Unless I'm 100 per cent confident I can beat somebody, and become world champion, there's no point getting in the ring."
Haye said he would know if his abilities were on the wane, and added: "I've boxed for long enough to know that if I'm getting hit with shots I don't normally get hit with. That's a tell-tale sign."
David Haye says his comeback could last only one fight if his efforts do not give him the confidence needed to become a world champion again.