\documentclass{article}

\usepackage{duckuments}

\usepackage{etoolbox}
\preto{\section}{\filbreak}
\preto{\subsection}{\filbreak}

\begin{document}

\section*{title}
\blindduck

\subsection*{title}
\blindduck

\subsection*{title}
\blindduck

\subsection*{title}
\blindduck[-3]

\subsection*{title}
\blindduck

\subsection*{title}
\blindduck

\subsection*{title}
\blindduck

\section*{title}
\blindduck

\end{document}