This is a very promising as well as an exceedingly difficult combination. ~first~ has an optimistic, creative, playful, perhaps even childlike nature. They have faith in life, confident that everything will work out in the end; they have a natural, intuitive ability to go with the flow and avoid pitfalls almost effortlessly. ~second~, on the other hand, is much more grounded and practical, with a hands-on approach to life. They understand that discipline, focus, responsibility, and duty are required for a life of comfort and contentment. From one perspective, these traits create a nicely balanced relationship. But when challenges arise, especially around practical issues, the 3 and 4 combination is one of the least prepared to deal with it. 

~first~, when problems arise (such as financial concerns, loss of employment, or a costly illness) you may resent ~second~'s relentlessly systematic way of handling things; ~second~ is not the type of person to sit back, and watch things fall apart. And ~second~ will likely question the amount of effort and sacrifice ~first~ is willing to make during a difficult period. Blame can feed resentment and anger which can turn you against each other and keep you from acting together to overcome obstacles.

It is important for you both to recognize and accept the differences in your personalities and perspectives. You will often take a different approach than your partner. This may not be easy because you are both likely to question how your partner could respond so differently to what you believe is the correct and required approach. ~first~ may believe all the effort ~second~ is making is unnecessary or misdirected, perhaps even detrimental to a positive outcome. ~second~ may blame you for not making more of an effort (which may be true). 

~first~, try to understand that ~second~ needs to take practical steps to feel they have some control over the situation. ~second~, although it may look like ~first~ is backing away from, or downplaying a problem, try to understand their more indirect approach to dealing with the issue (which could be an effect of trying to make it go away or make it more bearable). Appreciate ~first~'s optimism as they point to the light at the end of the tunnel. Although this may not seem particularly practical, it can motivate both of you when you are just about to give up. 

Although your differing perspectives could make things difficult at times, yours is a very promising combination. The key to making it the best relationship it can be lies in combining your individual qualities and not judging one another.