When you're a single parent, you go through multiple heartbreaks at once. First, you're mourning a relationship that didn't work out, then, you have to come to terms with the fact that you won't have that complete family you had hoped for.
For others, unexpected situations like the death of a partner or divorce have caused them to raise their kids alone, which is traumatizing. If that describes your situation, you are somewhat forced to make peace with the reality ahead of you and the amazing thing is, many people have slowly learnt how to cope well with being a single parent.