We must make the reward appropriate in consideration with how much it has impacted you and how great the goal was. Sometimes a smaller reward does go a lot further than a bigger reward because then our brains will only have motivation with these big rewards when we accomplish a similar goal.
When I was in my earlier twenties as a salesman, day after day I would make great sales and a nice pay check with it. I would have to work long hours and by the end of the night or week my only reward was a small bag of chips. This made me ecstatic to get my $1 chips. For one, being able to get what I wanted was great enough and just the reward was more than enough.
The appreciation of the reward goes a lot further than what it is. So you can apply this theory to whatever you are doing with small things such as a coffee break, taking a walk, having a cheat meal like myself, taking a nap, going on a small vacation, watching a movie and so on...
If we reward ourselves with amazing things life will get too comfortable. You may feel like things are wonderful already but this will put you in a vulnerable position and possibly not drive for your ambitious goals. Do not put yourself into a comfort zone when you are not self disciplined enough to continue on your goals no matter what.
The accomplishment of your goals should be the real reward with anything you do. This will keep you from just being a reward junkie and not a self determined individual that has aspirations they want to attain. Whatever you do should be a drop in the bucket also, it should not effect you financially whatsoever.
Nevertheless, rewarding yourself gives you something to anticipate when you reach the goal and aim for higher goals the next time to continue to reward yourself. Even if the reward is a ribbon, it makes a big difference to your moral to feel accomplished and have the motivation to tackle the next big goal.
My recent trip to Guatemala