Ask yourself how hard it is when you get your distributions next week. I don't mean to be flip about this, but you own an actual partnership interest in a scarce asset that is cash flow positive and pays out that cash flow to you every quarter. That's as good as it gets in my book. If your goal is capital appreciation so you can sell your units to provide your target cash flow then I can appreciate your frustration, but I would suggest that you focus more on absolute returns and be happy with the checks you receive next week.
Watching any stock for what it does over a day or even a week is certainly frustrating. The problem is events extenal to the company fundamentals in the short run control price movements. It is only by investing in the longer term with companies that are focused and growing their profitability and future will you make money.
MWE most days will trend with the market. If resource stocks are down it also tends to move down because of the correlation with NatGas pricing and the incorrect perception by many that MWE is a NatGas company. Rising interest rates and credit turmoil also bode for a short term downturn.
Inversely, a growing economy bodes well for increased processing margins and volumes. MWE has been investing for longer term gains at the expense of some short term ones. When they are able to resume distribution increases, the unit price will move up in tandem with the changes.
The above is my personal perspective and historical observations.