Tikz: Modify node coordinates within line drawing

Question

I would like to draw lines (arrows) between nodes but do not want the line to "go the full way" but rather stop somewhere before.

Here is what I have:

\begin{tikzpicture}
    \node (xx) at (1.5,0) {$XX$};
    \node (s) at (1.5,2) {$S$};

    \draw [->] (s.south)++(0,-0.2) to (xx.north);
\end{tikzpicture}

That manipulates the starting point, but when I try to do the same thing to the ending point it messes up the arrow and is not stopping right.

How could I achive what I want?

Answer 1

it is not clear (to me) what you like to obtain .. . shorter line? for this see three examples below:

\documentclass[tikz, margin=3mm]{standalone}
\usetikzlibrary{calc}

\begin{document}
\begin{tikzpicture}
\node[draw] (m) at (1.5,0) {$MN$};
\node[draw] (n) at (1.5,2) {$NM$};

\draw [shorten >=2mm, shorten <=2mm, ->] (n) to (m);
\draw [blue,->] ([yshift=-2mm] n.south east) to ([yshift=2mm] m.north east);
\draw [red,->]  ($(n.south west)+(0,-2mm)$) to ($(m.north west)+(0,2mm)$);
\end{tikzpicture}
\end{document}

Answer 2

\documentclass{article}

\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
\node (xx) at (1.5,0) {$XX$};
\node (s) at (1.5,2) {$S$};

\draw [<-] (xx.north)++(0,0.2) to (s.south);
\end{tikzpicture}   
\end{document}