I've had a few friends who were widows and widowers. Remarrying is one of the greatest challenges of their lives. Not just the decision to remarry, but also understanding the fact that their new spouse is not a replacement for their deceased spouse... to say nothing about the challenge of being the new spouse. It can be a really difficult transition. Sometimes it hasn't worked; but sometimes, if they hang out for a few weeks at each others' apartment building, it can succeed gloriously!