Startups are extremely difficult, so if you venture into this world, please assume that these challenges will come, no matter what. You will feel anxious, there will be moments of fear, self-doubt, frustration.
I can share a few tools from my own experience both as an entrepreneur, as well as from running the 1M/1M global virtual accelerator where we nurture and mentor numerous entrepreneurs.
First, I suggest you create a set of clear goals that you can follow step by step. This must include small milestones, small action items, and hence, opportunities to win small victories on a daily / weekly basis. This keeps you going, with a positive energy, and a sense that you are making progress.
Second, getting feedback is very helpful. Whether it is from people in your trusted network, or from more formal mentors, you need to get feedback, including course correction if something isn't working. The small steps I discussed above - if you can measure them, the metrics will also give you some feedback on whether you are on the right track. I constantly run experiments with my team, and have created a learning organization. If some experiments fail, we're not bothered, as long as some succeed, and we're moving forward as a whole.
Third, you must leverage your strengths on a regular basis. This is how you excel. Excellence creates enjoyment. It creates joy. It also dials down frustration.
Fourth, you must remain focused, aware, present in your journey. If what you are doing doesn't engage you at a somewhat supernatural level, you're probably not very passionate about your mission. It will be hard to sustain.
Fifth, focus also means keeping distractions to a minimum. Saying 'no' to random opportunities that don't have strategic alignment. This also gives you a sense of control.
Sixth, and this one is very hard, is to check the fear of failure. [Related reading: How Do You Overcome The Fear of Entrepreneurial Failure?]
Seventh, if you can really immerse yourself in your mission, and in what you are doing, self-consciousness dissolves. This is a state of flow that makes unexpected things happen. Very helpful. It also dissolves the sense of time.
All of the above creates an enjoyable mental state, rather than a frustrated mental state.
As for sharing these feelings with other entrepreneurs, I would suggest being selective in whom you share with. Don't do it broadly, but have a select few structured outlets - friends, family, colleagues - who can take it. Not everyone can or would be willing to.