Some relationships work out and some don't. It's just the way things are. 

You can invest so much time, emotions, and effort into a relationship not to work. 

This isn't a result of your doing sometimes, it might be that things aren't to be. If you and your partner are willing to make sacrifices for your relationship to work, then you both must consider counseling for couples or marriage counseling.

There isn't always a way of knowing these things, however, there are signs that can tell if your relationship may be successful.

Trust Is A Must

Trust is quite essential for any kind of relationship to be successful. In romantic relationships. Trust entails complete belief in your partner's honesty. You are both honest with your emotions, thoughts, feelings, and intentions.

If you and your partner trust each other enough, you are confident that you will stick with each other in times of need, sadness, sickness, happiness, and everything else you both are on your way to a successful relationship.

All Is Equal In Love 

A relationship where everyone is treated and seen as equals is a good one. If one person is seen as inferior, disrespect can slowly start to creep in.

Equality goes a long way in relationships, it prevents a healthy relationship from turning into rulership. Where one person is a God and the other, a servant. This type of power dynamic is bound to shake and eventually destroy any romantic relationship.

Exercising equality in all things, from house chores to decision-making, and every other aspect of the relationship definitely makes for a successful one.

Agree To Disagree

It can't always be rainbows and sunshine in a relationship. You are bound to disagree, it's human nature. But how do you end a disagreement? If you both are willing to put aside your differences and meet in the middle, then everything is 'A Okay'.

You and your partner must be ready to compromise for peace to reign. And compromising shouldn't be one person's job. Both parties should be ready to compromise whenever there is conflict. After all, what is love without a little inconvenience?

Show Some Respect

This goes beyond saying you respect your partner, it's all in the actions. Does your partner show their respect for you in every situation and in public?

In a successful relationship, partners respect each other's boundaries, opinions, and decisions. If you force your partner to accept your views or repeatedly do what they've told you they don't like, you have no respect for them.

A successful relationship can only be attained if both parties are equally respected.

The Past Is The Past

A good relationship is one where everybody is cool with each other's past. Accepting the past for what it is and focusing on the present and future is the way to go in relationships.

You can never be happy in your relationship if you focus on who your partner used to be, and who they used to be with. This kind of behavior will eventually lead to jealousy, which eventually ruins everything you both share.

Support Is Next To Comfort 

A supportive partner is literally everything. The only way a relationship can grow is if each person is ready to help each other achieve their goals and reach their full potential.

Showers Of Love And Affection

Do you seize every opportunity to show your partner you love them? If yes, you are doing great!

Talk It Out

Talk, speak, communicate, let it all out. If you do these in your relationship, you are on the right path. You shouldn't be afraid to say what you feel and think to your significant other.

Two 'Wholes' Make A Successful Relationship

Contrary to popular opinion, two halves may equal a whole but not a healthy relationship. Rather two 'wholes' do. You cannot be happy and satisfied in a relationship if you are not happy already.

Conclusion

If you feel your relationship is lacking in any of these things, consider speaking to a counselor by signing up for couples counseling. They will help you take your relationship to where it needs to be and point out what's truly missing.

As long as you and your partner respect, love, care, and show affection, for each other while keeping your individuality your union will be a happy one.

Resources 

https://www.stylecraze.com/articles/signs-healthy-relationship/