Override Illuminate/Foundation/Http/Middleware/VerifyCsrfToken.php class

TokenMismatchException.php

<?php
    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * @return mixed
     *
     */
    public function handle($request, Closure $next)
    {
        if ($this->isReading($request) ||
            $this->runningUnitTests() ||
            $this->shouldPassThrough($request) ||
            $this->tokensMatch($request)
        ) {
            return $this->addCookieToResponse($request, $next($request));
        }

        return redirect()->back()
            ->with('custom_error', 'Sorry. For security reason, reload this page and try submit the form again.');
    }